Organic Chem Flashcards
1
Q
cWhy is carbon 14 so special
Whats a hydrocarbon
A
It can form 4 covalent bonds with other carbon atoms. These can be single double and triple and these can form long chains
Compound containing C and H
2
Q
Difference between saturated and unsaturated hydrocarbons
A
Saturated-single bonds only
Unsaturated- has carbon to carbon multiple bonds
3
Q
What’s a homologous series
What’s a functional group
A
A family of compounds with similar chemical properties whose successive members differ by the addition of a -CH2- group.
Part of the organic molecule that is largely responsible for the molecules chemical properties
4
Q
How many covalent bonds do hydrogen carbon and oxygen make
And what can them bonding to other things mean
A
C-4
O-2
H-1
Results in formation of molecules containing different functional groups
5
Q
Who recognised the need for standardisation of the name of compounds
A
IUPAC
6
Q
What is an aliphatic hydrocarbon
A
Carbon atoms joined to each other in unbranched or branched chains /or non aromatic rings
7
Q
What are alicyclic hydrocarbons
A
Carbon atoms joined to each other in ring structures with or without branches
8
Q
What are aromatic hydrocarbons
A
Some or all of the carbon atoms are found in benzene rings
9
Q
What are the three homologous series of aliphatic hydrocarbons
A
Alkanes-has one carbon to Carbon single bond
Alkenes- has one carbon to carbon double bond
Alkynes-has one carbon to carbon triple bond
10
Q
What does the stem of the name indicate
What does the prefix indicate
What does the suffix indicate
A
Stem-no of carbon atoms in the longest continuous chain of the molecule
Prefix-added before stem to indicate presence of side chains or functional groups
Suffix- added after stem to indicate functional groups
11
Q
What’s an alkyl group
Formula for alkyl groups
Names of the first 10 alkyl groups
A
Alkane missing one hydrogen
CnH2n+1
Methyl
Ethyl
Propyl
Butyl
Pentyl
Hexyl
Heptyl
Octyl
Nonyl
Decyl
12
Q
How to name unbranched alkenes-aliphatic
A
Look at where the double bond is between the carbons
Number the carbons and choose the lowest of the numbers to place the number
Eg
H-C-C-C=C-H
H H
This is butene
The double bond is between 3 and 4 but if u reverse it it’s between 1 and 2 u choose the lowest one which is one so it’s called but1ene
13
Q
What’s the name of this aliphatic hydrocarbon
H H H H H H
H-C-C-C-C=C-C-H
H H H H
A
Hex2ene
14
Q
How to name branched alkanes
A
Find the suffix based ON LONGEST C CHAIN
Find suffix for side chains
See what number side chain is attached to
If there’s two side chains it’s di
Eg
H
H-C-H 7 so it’s heptane
H H | H H H H. One C in side chain
H-C-C-C-C-C-C-C-H. So methyl and side
H H H H H H H Is on 3rd one so it’s 3methylheptane.
15
Q
What’s this molecule called
H-C-H
H H|H H H H
H-C-C-C-C-C-C-C-H
H H H H | H H
H-C-H
H
A
3,5 di methylHeptane
16
Q
What’s this one called
H
H-C-H
H-C-H
H H | H
H-C-C-C-C-H
H H H H
A
5 is suffix number so pent
Side chain only has 1 so methyl
Found on carbon 3
So 3 methylpentane
17
Q
What if there’s two side chains and they’re not the same
A
Same thing but u name is alphabetically
So 3 methyl and 5 ethyl
It will go 5 ethyl first
5 ethyl3methylpentane
18
Q
Name this branched hydrocarbon
H-CCCCCCCCC-H
Flahscard
A
FLASHCARD
19
Q
Name this branched alkene
A
20
Q
When it’s alicyclic alkane what’s the prefix u put in front
A
Cyclo
21
Q
Definition of molecular formula
And empirical formula
A
The actual number of atoms of the elements in that compound
The simplest whole number ratio of the atoms of each element present in a compound
22
Q
Downside of molcuelsr formula
A
Doesn’t give us any info on structure of molecule/how the atoms are bonded to each other
Different molecules can have same molecular formulae
23
Q
What’s the functional group prefix and suffix for
Alcohol
Haloalkane
Aldehyde
Ketone
Carboxylic acid
Ester
Acyl chloride
Amine
Nitrile
A
OH,hydroxy,ol
Cl br I,chloro bromo iodo,
CHO, ,al
C(CO)C, ,one
COOH, OIC acid
COOC. ,oate
COCL, Oyl chloride
Nh2, amino, Amine
CN, Nitrile
24
Q
What’s the displayed formula and a downside
A
Shows the relative positioning of all of the atoms in a molecule and the bonds between them
They don’t show accurate bond angles
25
What’s structural formula and give downside
Uses smallest amount of detail necessary to show arrangement of atoms in a molecule
Doesn’t show us the bonds but shows us which groups are bonded together
26
If we need to show a side chain in a structural formula what do we do
Put it in brackets and put it after the carbon it’s attached to
27
In the skeletal formula what do u show and not show
You don’t show the carbon and hydrogen labels and any bonds to H atoms
You show the carbon skeleton and any functional groups
28
Skeletal formula of 2methylhexane
2chlorobut1ene
2methylpentan3one
FLASHCARD
29
What’s the general formula
The simplest algebraic formula for a member of a homologous series
30
What’s the general formula for
Alkanes
Alkenes
Alcohols
Carboxylic acids
Ketones
CnH2n+2
CnH2n
CnH2n+1OH
CnH2nO2
CnH2nO
31
What are structural isomers
Compounds with the same molecular formula but different structural formula
32
Draw the structural isomers for c4H10
And c5h12
Phone
Pentane methylbuyane and dimeyhylpropane
33
Why is ethylpropane not a isomer of c5h12
Name is based on longest carbon chain and longest is 4 so it’s acc methylbuyane
34
How many covalent bonds do
Carbon
Hydrogen
Oxygen make
4
1
2
35
36
What’s the displayed formula and structural formula of propan1ol and propan2ol
Displayed -phone
Structural-CH2(OH)CH2CH3
CH3CH(OH)CH3
37
38
Structural isomers of 1 chlorobutane
Phone
39
Why are alkanes interactive molecules
They are non polar as carbon atoms and H atoms have very similar electronegativity so as they’re non polar it’s unreactive
Bonds in alkanes are very strong and take a lot of energy to break
40
41
How can alkanes react
Via free radicals
42
What is a free radical
Any species with an unpaired electron
And they’re highly reactive and neutral
43
How can covalent bonds be broken
Homolytic fission or heterolytic fission
44
How does homolytic fission work
Each of the bonded atoms takes one of the shared pair of electrons from the bond
So each atom now has a single unpaired electron which is a radical
45
How does heterekytic fission work
When a covalent bond breaks by heterolytic fission one of the bonded atoms takes both of the electrons from the bond
The atom that takes both electrons becomes a negative ion
The atom that doesn’t take the electrons becomes a positive ion.
46
What’s the homolytic fission equation for the carbon carbon bond in ethane
And heterolytic fission of carbon - chlorine bond in chloromeghane
H3C-CH3–H3C• + •CH3
H3C-Cl-H3C+ + •Cl-
47
What’s a reaction mechanism
Provide info how the reaction takes place
48
In a reaction mechanism what do curly arrows show
When do we use half arrows
The movement of electron pairs when bonds are broken n made
In homolytic fissions representing movement of single unpaired electrons
49
Draw reaction mechanism of the homolytic fission of a carbon - hydrogen bond in methane
Phonr
50
What is an addition reaction
When two reactants join together to form one product
Eg but2ene and water add together to form butan2ol.
51
What’s a substation reaction and draw one for haloalkane 1-bromopropane
What’s nuceophile
An atom or group of atoms is replaced by a different atom or a group of atoms.
Search it up
a nucleophile is a chemical species that forms bonds by donating an electron pair to an electron poor species
52
What’s an elimination
Involves the removal of a small molecule from a larger one. One reactant molecule forms two products
53
3 ways structural isomers can be formed
1)alkyl groups in diff places
2)functional groups bonded to diff parts
3)different functional groups
54
How is a covalent bond formed from two radicals
Radicals collide and electrons are involved in bond formation
55
What’s an alkane
Saturated hydrocarbons containing C-H bonds only
CnH2n+2
56
Shape and angle of an alkane and why
Tetrahedral 109.5
Each C atoms surround by 4 electron pairs in 4 sigma bonds.repulsion between pairs results in tetrahedral with 109.5
57
How has crude oil deposits from alkanes allowed em to stay like that for many years
What are alkanes used for
Because theirAlkanes are very stable molecules.
They have only single bonds (C–C and C–H), which are not very reactive under normal conditions.
Fuels
58
Describe the bonding in alkanes
Each C atom is covalently bonded to 4 other atoms and these covalent bonds are called sigma bonds.
Covalent bond is a shared pair of electrons and these signs bonds are the result of overlap of orbitals from adjacent atoms.
A sigma bond contains a pair of electrons,one from each atom on either side of bond
And pair lies directly between bonding atoms
59
What causes alkanes to rotate freely
Free rotation across The sigma bonds which acts as axes allowing them to rotate and not be rigid
60
What do alkane combustion reactions release and why are alkanes used as fuels
Oxygen and water
Because they’re readily available,easy to transport and. Burn in a plentiful supply oxygen without releasing toxic products
61
What’s the formula to balance the complete combustion of any alone
CxHy+(x+y/4)O2—xCO2+y/2 H20
62
What happens when oxygens limited in combustion
Incomplete combustion occurs where hydrogen atoms are always oxidised to water but combustion of carbon is incomplete forming co or soot(C).
It’s harder to combust in spaces where o2 is harder to reach
63
what is carbon monxodie and write equations for incomplete combustion of methane
Colourless odourless toxic gas
Ch4+1/2O2—-Co+2H20 or the normal one yk
64
What is complete combustion and incomplete combustion
Complete- combustion that occurs with plentiful supply of air
Incomplete-combustion in a limited supply of oxygen
65
66
What type of reaction is combustion and what’s the colour of Bunsen burner flame during complete combustion .
Oxidation
Blue
67
What type of hydrocarbons are most likely to undergo incomplete combustion
Longer chain
68
Environmental impact of soot
Asthma,cancer,global dimming
69
How are halogenoalkanes formed from alkanes
Radical substitution
70
In the presence of what does alkane react with halogens
Uv light from sun
71
What’s the reaction mechanism for radical substitution
1)initiation
Covalent bond in bromine molecule broken by homolytic fission
Each bromine atom takes one electron from the pair forming two highly reactive bromine radicals . Energy for bond fission given by uv
Br—br—-Br• + •Br
2)Propagation-proppagates through two propagation steps
In first P step, bromine radical reacts with a C-H bond in methane forming a methyl radical •CH3 and Hbr
Ch4+Br•—Ch3+Hbr
In second P step,each methyl radical reacts with another bromine molecule forming CH3Br with a new bromine radical Br•
Ch3+Br2—Ch3Br+Br•
New Br• continues to react with another Ch4 and two steps continue in a chain reaction.
3)Termination-two radicals collide forming a molecule with all electrons paired.when two r collide both radicals are removed from reaction mixture stopping reaction.
Br• + •Br—Br2
CH3 + •CH3—C2H6
Ch3 + •Br—CH3Br
72
Write equations for reaction of ch4 with cl2 to form Ch3Cl
Initiation:Cl2–2Cl(w UV light)
Prop:Cl• + CH4—HCL+•CH3
•Ch3 +Cl2–Ch3cl + Cl•
Termination-
•CH3 + Cl•—CH3Cl
2Cl•—Cl2
•CH3+ •CH3—CH3Ch3
73
Limitation of radical substation
It can limit he synthesis of just one organic compound
74
3 possible reactions in terminations
Two bromine free radicals can form a bromine molecule
Two methyl free radicals can form a molecule of ethane
Methyl free radicals and bromine molecule can form a molecule of bromomethane
75
At end of reaction why do we need to seperate out our product molecules
Side products could be made
Eg •Br could react with bromomethane to form dibromomethane
And further reacts with tri and tetra
Also we make ethane and that could also react with •Br to form more molecules
If this reaction carried out with longer chain molecules too we get mixture of monosubsitutyred isomers at diff parts of carbon chain
76
77
How is crude oil separated
Fractional distillation-due to alkanes having different BPs
78
Why does Bp of alkanes increase
Alkanes have Weak intermolecular forces called LF due to the bonds being nonpolar and the greater the LF the higher the BP
79
What happens to boiling point as alone chain length increases
LF acts between molecules that are involved close surface contact so as chain length increases,higher SA, so more surface contact between molecules.also they increase with electrons so ya LF between molecules greater(more induced dipole dipole interactions) so more energy required to overcome attraction.HIGH BP
80
Does a branched molecule have a lower or higher boiling point compared to equivalent straight chain? Why
Branched molecule has lower BP as it has a lower sa so fewer surface points of contact between molecules so lower LF
Branches also get in way and prevent branched molecules getting as close together as straught chain molecules decreasing LF further
81
Why don’t alkanes react
C-C and C-H sigma bonds are strong
C-C bonds are non polar
Electronegativity of C and H so similiar C-H bond is non polar
82
Why are alkanes insoluble
Water molecules form hydrogen bonds with each other
And these hydrogen bonds which acts are stronger than the alkanes LFs
83
What reactions with alkanes undergo
Combustion and reaction with halogens
84
What are Alkenes
Unsaturated hydrocarbons that contain at least one C=C bond made of a pi and sigma bond
They have the general formula cnh2n
85
86
What happens to the strcutre when Alkenes become cyclic or have more than one double bond
They don’t follow the CnH2n formula anymore as presence of additional double bonds reduces no of hydrogen atoms needed to saturate the carbon chain and cyclic doesn’t have it as u need to remove two H atoms from linear chain to close the loop so it’s bsc cnh2n-2.
87
What the nature of the double bond
So each c atom has 4 e- in outer shell which can be used to form bonds. 3 of them is used in sigma bonds. One for the C atom and the other two for the other two atoms (C/H)
Leaving one electron on each C atom of double bond in p orbital
A Pi bond formed then by sideways overlap of two P orbitals from two carbon atoms contributing one electron. Can only happen after sigma bond formed
88
Where is the Pi electron density situated
Above and below line joining the nuclei of both bonding atoms
89
What bond restricts the rotation of carbon atoms
Pi bonds. It locks them in position and prevents them from rotating around which is a big difference to alkanes where rotations possible around every atom.
90
What’s the shape of a double bond n whyyy
Triagonal planar as:
1)There’s three regions of electron density around each of the carbon atoms
2)3 regions repel as far as possible so bong angle around each C atom 120c.
3)All of the atoms are in same plane
91
Are Alkenes more reactive than Alkanes
Yes due to the double bond being unstable cuz of high electron density of the double bond as its electron rich due to pi bonds and concentrated above n below the plane of sigma bond so pi electrons are more exposed than sigma electrons as they're less tightly held comp to sigma bonds which tightly held between nuclei so the pi bond is easier to break. So it can react more easily. doible bond is also unstable
This makes alkenes more susceptible to addition reactions.
92
What intermolecular forces of attraction do Alkenes have
London forces due to non polar bonds (from C-H making whole molecule non polar)
93
Are Alkenes soluble in water
No they have non polar bonds
94
Why may alkenes produce more soot than alkanes
Due to the presence of the double bond with a higher C:H ratio.
95
What are stereoisomers
They have the same structural formula but different arrangement of atoms in space
96
Two types of isomers formed usinf alkenes
E/Z isomers- due to the restricted rotation
Cis-trans isomers- if two of the same substitutes are attached to each carbon
97
What are the requirements for cis trans isomers
Molecules must have a C=C double bond and each C in double bond must be attached to two different griups. And one of the attached groups on the C atom must be a hydrogen
98
What’s the difference between the cis isomer and trans isomer
Cis has the hydrogen atoms on each carbon in double on the same side of molecule whereas trans isomers have hydrogen atoms diagonally opposite each other
The cis isomer is the Z isomer
And trans isomer is the E isomer
99
What’s an example of a cis trans isomer and draw it
Bu2ene phone
100
Why does stereoisomerisn occur around double bonds
Due to rotation around a double bond being restricted and groups attached to each carbon atom are therefore fixed relative to each other
Rigidity is due to position of pi bond electron density and above and below plane of sigma bond
101
What are the conditions for E/Z isomerism
A double C=C bond
And different groups attached to each carbon atom of the double bonds
102
Why can bu1ene not be a E/Z isomer
Because it doesn’t satisfy the condition where different hroups attached to each carbon atom of double bond
103
Limitation of cis trans system
It can only be used when each carbon atom in double bond is attached to a single hydrogen atoms. When theres different groups we can use E/Z system
when there are three or more different groups attached to the double bond, as it becomes ambiguous which groups are considered "cis" or "trans"
104
How do we use the E/Z system
Through the CIP rules:
Atoms are given priority based on atomic number
If atoms given priority are on same side of double the compound is Z isomer
If atoms given priority are diagonally placed across double bond, it’s E isomer.
105
When tryna find atomic number and comparing it you could reach a point where the molecules are the same across two branches what do u do
Move onto the next atom until u reach a point of differebce
106
107
What may Alkenes undergo addition reactions with
Hydrogen in presence of nickel catalyst
Halogens
Hydrogen halides
Steam in presence of acid catalyst
They require addition of a small molecule across the double bond causing pi bond to break n for new bonds to form
108
What’s the conditions for hydrogenation of alkenes
Alkene+hydrogen w a nickel catalyst at 423K
Addition reaction takes place to form alkane
This addition reaction where given added across double bond is hydrogenation
109
Draw hydrogenation of propane
Pphjjooooneeee
110
When a molecule w c=c bonds reacts with hydrogen in this way what happens when it has more than one double bond
Draw hydrogenation of buta1,3-diene
It would need two molecules of hydrogen per molecule.
111
What happens with halogenation of Alkenes
Alkenes undergo quick addition reaction w halogens (Cl/Br) at rtp
112
Why don’t Alkenes undergo halogengaion with any other halogens
Fluorine’s extremely reactive so hard to control reactions
Iodine can be underreactive
Br and Cl are a good balance
113
Halogentaion of bromine with propene
Phone
114
How to test for unsaturation
Bromine test to test if C=C present and if it’s unsaturated . When bromine water (orange)added drop wise to alkene bromine adds across double bond and colour dissapears showing presence of C=C bond. Negative test would be no colour change
115
What happens when Alkenes react with hydrogen halides
Form haloalkanes at rtp.if Alkenes is a gas the reaction takes place (ethene)when two gases mixed.if alkene liquid then hydrogen halide bubbles through it.
They also react w concentrated HCL or concentrated hydrobromic acid.
2 possible products formed
116
Reaction of proper with hydrogen chloride
Phone
117
Hydration reaction with alkenes
When Alkenes react with steam they make alcohol. In presence of phosphoric acid catalyst H3Po4. Steam added across double bond.There are two possible products
118
What’s an electrophile and
what attracts them
Any positive ion or molecule that is attracted to electron rich centre and accepts an electron pair
High electron density of pi electrons.
119
What’s the addition reaction between but 2 ene and hydrogen bromide
Phone
120
Why do hydrogen halides have a permanent dipole
Because halogens are way more electronegative than hydrogen including a dipole
121
How does electrolytic addition happen with but2ene and hydrogen bromide
First hydrogen bromide molecule approaches the alkene.Positve hydrogen in HBR attracted to the high electron density of the double bond. It’s the electrophile lol. Positive charge of H aayracts the electrons in the pi bond of alkene . This pair of electrons move towards the H. You draw curly arrow to show this.H atom can only have one covalent bond so pair of electrons in covalent bond between H and Br now move onto bromine atom. Show w arrow When covalent bond breaks with both electrons going to one atom (br)it’s called heterolytic fission.
Carbocation intermediate formed which is positively charged as C is positively charged due to it losing its share of the electron pair that was in the pi bond.Negatively charged bromide ion also formed and this is negatively charged as both electrons that were in covalent bond now in bromide ion. Now the electron pair on bromide ion is attracted to the positive carbon in carbocation. Now this forms the product 2 bro butane
122
In an smectrophilic addition reaction the alkene that reacts w the halogen halide is symmetrical what happens ans what happens when its asymmetrical
If it’s symmetrical then only one product is made
If it’s asymmetrical the 2 products made
123
In what reactions does electrophiluc addition happen
When alkenes take part addition reactions to form saturated compounds.
124
Draw the electrophilic addition reaction between but2ene and hbr
Phone
125
What happens when Alkenes react with non polar molecules like Br
Bromine adds to propene to form single addition product.
As its non polar bromine molecule approaches alkene and pi electrons interact w electrons in the BR—Br bond. This interaction causes br-br to become polar w one end being br&- and other br&+. Induced dipole.
The electron pair in the pi bond is attracted to the br&+ end of molecule causing double bond to break
A bond now formed between one of C atoms from double bond n bromine atom.Br—Br breaks by heterolytic fission. W electron pair going to Br&- end of molecule
Bromide ion and carbocation made
The br- ion reacts with carbocation to form addition product of reaction
126
Draw the electronic addition between propane and bromine
Phone
127
What’s markownikoffs rule
When hydrogen value reacts w unsymmetrical alkene hydrogen of hydrogen halide attached myself to carbon of alkene w greatest number of hydrogen atoms and least c atoms
So when propene reacts w HBR it will form two carbocations and the positive garage will be on carbon at end of chain first and in second carbocation positive charge will be on carbon w two carbon chains attached. So major product is the second carbocation 2 bromopropane.
128
What is an alkyl represented by and which carbonation are the most stable
Letter r
Tertiary-with three r groups
Primary least.
129
What are carbocations classified by
The number of alkyl groups attached to positively charged C atom.
And the electron donating ability of the alkyl groups.
Each alkyl group donates and pushes electrons towards positive charge of carbocation. It’s spread over alkyl groups .
The more alkyl hrouos attached to positively charged c atoms more charge spread out making ion more stable
So tertiary is the most stable
130
Whats a polymer
When does addition polymerisation occur
Large molecules formed from many repeating units called monomers
Unsaturated molecules go under it to form long saturated chains with no double bonds.
At high temp n high pressure with catalysts
131
What is an addition polymer
What are monomers
What form do they take
Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule.
Molcules combining to form polymer
C=C bond which breaks to form repeating pattern
132
What’s a repeat unit
The specific arrangement of atoms in polymer that repeats over n over
133
Most commonly used polymer and what’s is used in
Polyethene
Bags shampoo bottles and toys.
134
Draw polymerisation of polyetehne
H H [ H H ]
| | [-C—C— ]
C=C ——[ H H ]
| |
H H
135
What’s poly chlorethene used for
Polypropene
Polyphenylethene/Polystyrene
Polytetrafluroethene/teflon
Make polymer that’s flexible n rigid like pipes films ducts
Toys fibres for ropes and crates
Packaging material and cups and food trays cuz it’s thermal insulating
Coating for non stick pans and insulation
136
Draw equations for pvc
Polypropene
Polystyrene
Teflon
Look book
137
Environmental waste concerns (3)
Disposing of waste polymers- polymers are readily available cheap and convinient than paper bags and cardboard etc.unreactivity of polymers makes it suitable to store food and chemicals safely BUT they’re alkene based polymers - non biodegradable and growing polymer waste can kill marine life
Recycling Polymers conserves finite fossil fuels and dec waste to landfill.Theyre sorted by type as if it’s mixed it’s unusable and then it’s chopped dried n melted and remade.
PVC recycling-is dangerous due to high chlorine content and range of additives in polymer.dumping in landfill is not sustainable and if burnt it releases hydrogen chloride corrosive gas n other pollutants
We grind pvc and reuse it to manufacture new products. New tech dissolves polymer. PVC recovered from precipitation from solvent and solvent reused
Using waste polymers as fuel- as some polymers from petrol n natural gas they have Hugh energy storage value
Polymers can be incinerated to make heat making steam to drive turbine to make electricity.
138
Environmental concerns (3)
products from feedstock recycling resemble those made from crude oil in refineries. These materials used as raw materials for new polymers.Adv is that it can handle unsorted + unwashed polymers.
Bio plastics-made from cellulose starch plant oils proteins and offer a renewable n sustainable alternative to oil based products. It protects env and conserves valuable oil reserves
Biodegradable polymers-broken down by microorganisms into water, co2, and biological compounds. These polymers are usually made from starch or cellulose, or have additives that alter the structure of traditional polymers so that microorganisms can break them down.
Compostable polymers degrade and leave no visible or toxic residues.
Compostable polymers based on poly (lactic acid)are becoming more common as alternative to alkene-based polymers.
Supermarket bags made from plant starch used as bin liners for food waste waste and bag can be composted together.
Compostable plates, cups, food trays made from sugar cane fibre are replacing expanded polystyrene. As the technology advances, bioplastics are likely to be more used in packaging, electronics, and more fuel-efficient and recyclable vehicles.
Photodegradable polymers
Where use of plant-based polymers is not possible, photodegradable oil-based polymers are being developed. These polymers contain bonds that are weakened by absorbing light to start the degradation.
Alternatively, light-absorbing additives are used.
139
Functional group of alcohol n what its responsible for
And general formula
OH-hydroxyl group-both the physical n chemical properties of the alcohol
CnH2n+1OH
140
Name this alcahol
H H H H
| | | |
H-C—C—C—C—H
| | | |
H OH OH H
2methylbutane-2,3-diol
141
142
Differences between alachols and alkenes
Alcahols are less volatile,have higher Bp and greater water solubility than corresponding alkanes
These can be explained by the polarity of the bonds and the effect they have on strength of IM forces
143
Bonding differences between alcahols n alkanes
alkanes have non-polar bonds because the electronegativity of H and C are very similar.
• The alkane molecules are therefore non-polar.
• The IM forces between non-polar molecules are very weak London forces.
• Alcohols have a polar O—H bond because of the difference in electronegativity of the O and H atoms.
• Alcohol molecules are therefore polar.
• The IM forces will be very weak London forces but there will also be much stronger hydrogen bonds between the polar O-H groups.
144
Why does alcahols have more volatity and higher bp
In liquid state Intermolecular hydrogen bonds hold the alcohol molecules together.These bonds must be broken in order to change the liquid alcahol into a gas . This requires more energy overcoming the weaker London forces in alkanes so alkanes have a lower volatility and higher Bp than alkanes with same number of carbon atoms
145
Why are alcahols are more watersoluble than alkanes
Alcahols can form hydrogen bonds with water alkanes can’t. Alkanes are non polar .alcahols are soluble in water as H bonds form between polar OH group of the alcohol and water molecules. As hydrocarbon chain increases in size,the influence of the -OH group becomes relatively smaller and the solubility of longer chain alcohols become more like that of hydrocarbons and solubility decreases.
146
Draw a diagram of hydrogen bonds forming between methanol n water
PHONE
147
If a compound has a lower boiling point what can be said about its volatity
The lower the BP, the higher the volatity =more easily converted from a liquid to a gas.
148
How to classify alcahols
alcahols can be primary secondary or territory and this can be based on
The number of hydrogen atoms and alkyl groups attached to the carbon atoms that contain the alcahol functional group.
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How to become a primary alcahol
The OH group is attached to a carbon atom that is attached to 2 Hydrogen atoms and 1 alkyl groups.
Eg methanol(exception w 3 H is an exception),ethanol
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How to become a secondary alcahol
The -OH group is attached to a carbon atom that is attached to 1 hydrogen atom and 2 ALKYL groups.eg propan2ol and pentan3ol
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How to become a tertiary alcahol
The OH group is attached to a C atom that’s attached to NO hydrogen atoms and 3 alkyl groups
Eg 2methylpropan2ol and 2methylbutan2ol
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Propane-1,2,3-trios is more soluble in water than propan1ol why?
Propane- 1,2,3-triol has three -OH groups in its structure. Each OH groups is able to form hydrogen bonds with water molecules. The more hydrogen bonds formed between a molecule and water the greater the solubility.
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What happens when alcahols are burnt
When they burn completely in a plentiful supply of O2 it makes CO2 n H20.It’s exothermic realising a lot of energy as heat.As number of C atoms in alcahol chain increases the quantity of heat released per mole also increases.
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write an equation for combustion of ethanol
c2h5oh(l)+3O2(g)--2CO2(g)+3H20(l)
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what can primary n secondary alcohols be oxidised by
an oxidising agent=usually potassium dichromate(VI) k2cr2o7acidified w dilute sulphuric acid h2so4.
if alcohols oxidised the orange solution containing dichromate ions is reduced to a green solution containing chromium ions(111)
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what can primary alcohols be oxidised to form
aldehydes(formed from partially oxidising) or carboxylic acids(forms from fully oxidising)
depends on reactions conditions used
as aldehydes can be oxidised themselves to carboxylic acids.
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how is an aldehyde made
gentle heating of primary alcohols w acidified potassium dichromate(dilute sulphuric acid used) an aldehyde is formed.to ensue an ALDEHYDE formed than carboxylic acid aldehyde distilled out of reaction mixture as it forms.This prevents any further reaction w the oxidising agent. dichromate ions change colour from orange to green
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show the oxidation of butan1ol
phone
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how is a carboxylic acid made
when a primary alcohol heated strongly under reflux with an excess of acidified pottassium (strong sulphuric acid used)dichromate.
excess acidified potassium dichromate ensures that all of the alcohol is oxidised.heating under reflux ensures that any aldhehyde formed initially in reactions undergoes oxidisation to become carboxylic acid
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show the complete oxidation of butan1 ol
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what does heated under reflux mean
boil the mixture while a condenser cools n returns evaporated solvent back to the reaction flask so nothings lost(to ensure aldehyde remains in reaction mixture and is fully oxidised to carboxylic acid.
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what are secondary alcohols oxidised to
ketones and its not possible to further oxidise ketones w acidified dichromate ions.to ensure reaction goes to completion ketones heated under reflux w oxidising mixture.dichromate ions once again change from orange-green.
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show the oxidation of propan2ol
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oxidation of tertiary alcohols
they don't undergo NO OXIDATION BITCHHH.acidifed dichromate remains orange when added to tertiary alcohol.
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write an equation for the partial oxidation of ethanol
write an equation for the full oxidation of ethanol write an equation for the oxidation of propan2ol
CH3CH2OH(l)+[OH]---CH3CHO(g)+H20(l)
CH3CH2OH(l)+2[OH]---CH3COOH(g)+H20(l)
CH3CH(OH)CH3(l)+[OH]--CH3COCH3(g)+H20(l)
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what's dehydration
which a water molecule is removed from the starting material.
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how is an alcohol dehydrated
alcohol is heated under reflux in the presence of an acid catalyst such as concentrated sulphuric acid,H2SO4 or conc phosphoric acid h3po4.this makes an alkene n water. 170oc
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what is dehydration of an alcohol an example of
elimination reaction.
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show cyclohexanol being dehydrated
phone
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what do alcohols react w to make haloalkanes
hydrogen halides.
to do this alcohol is heated under reflux with sulphuric acid and a sodium halide and the HBR formed in situ(in place).
Nabr(s)+H2SO4(aq)---NaHSO4(aq)+HBR(aq)Hbr formed reacts w the alcohol to produce the haloalkane
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what reaction is alcohols +hydrogen halides
substitution reaction
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show the reaction of propan2ol with Hbr.
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what are haloalkanes
compounds containing carbon,hydrogen and at least one halogen.
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are haloalkanes polar
haloalkanes have a carbon-halogen bond in their structure.halogen atoms are more electronegativity than c atoms.electron pair in carbon halogen bond is therefore closer to the halogen atoms in carbon atom.The carbon halogen bond is polar
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are haloalkanes soluble in water
insoluble as for a haloalkane to dissolve in water, the IM forces between the h20 molecules (H bonding) need to be replaced by similar interactions with the haloalkane molecules. But haloalkanes don't form H bonds, + their dipole-dipole interactions with water molecules are not strong enough to break the hydrogen bonding network in water.
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what IM forces do haloalkanes have
London forces and permanent dipole dipole-CX bond polarity creates this.
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when would haloalkanes have higher boiling points
inc carbon chain length further down group 7
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how would the mass of an alkane compare w the mass of a halogen of the same length
mass of halogen is bigger than mass of alkane=alkane made only of (C) + (H) atoms. The molecular mass of an alkane inc w the no of c atoms, as each c contributes a mass of about 12 g/mol, and each H atom contributes about 1 g/mol.
A haloalkane is formed by substituting one of the hydrogen atoms in the alkane with a halogen atom (e.g., chlorine, bromine, or iodine). The halogens are much heavier than hydrogen.
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most important factor in determining halogen reactivity
strength of carbon halogen bond
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what would bond polarity suggest order of reactivity would be
what would bond enthalpies suggest order of reactivity would be
CF most reactive as most polar bond
CI most reactive as lower bond enthalpy
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what's a primary haloalkane
halogen present at end of chain
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what do haloalkanes attract
nucleophiles due to the c atom having a slightly positive charge and can attract nucleophiles
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what's a nucleophile
a nucleophile is an atom or group of atoms attracted to an electron deficient C atom where it donates electrons to form a new covalent bond (donor to poor)
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what do nucleophile include
hydroxide ions=:oh-
water molecules=h20:
ammonia molecules=:nh3
cyanide=:cn-
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what happens when haloalkane reacts w nucleophile
what's substitution
nucleophile replaces the halogen in a substitution reaction.a new compound formed containing diff functional group=nucelophilic substitution.
primary haloalkanes undergo this w loads of diff nucleophiles to make diff compounds.
when an atom or group of atoms gets replaced by another atom or group of atoms
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what's hydrolysis
chemical reaction that involves water or aqueous solution breaking a bond in a molecule.resulting in molecule being split into 2 products.
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hydrolysis in haloalkanes
halogen atom replaced by a oh- group.this is nucleophilic substitution
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how does nucleophilic subsutitio work
1)The nucleophile, OH, approaches the carbon atom attached to the halogen on the opposite side of the molecule from the halogen atom (Figure 3).
2)This direction of attack by the OH- ion minimises repulsion between the nucleophile and the &- halogen atom.
3)A lone pair of electrons on the hydroxide ion is attracted and donated to the + carbon atom.
4)A new bond is formed between the oxygen atom of the hydroxide ion and the carbon atom.
5)The carbon-halogen bond breaks by heterolytic fission.
6)The new organic product is an alcohol. A halide ion is also formed.
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draw the nucleophilic substation for hydrolysis of chloroethane
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how can haloalkanes be converted to alcohols
using aqueous sodium hydroxide.Reaction very slow at RTP so the mixture is heated under reflux to obtain a good yield of product.
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what's the equation for the hydrolysis of 1 bromobutane
CH3CH2CH2CH2BR+NAOH---CH3CH2CH2CH2OH+NABR
1bromobutane-butan1ol
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what does rate of hydrolysis depend upon
strength of carbon halogen bond in the haloalkane.in hydrolysis the carbon halogen bond is broken and the OH group replaces the halogen in the haloalkane.
btw The larger the value of bond enthalpy the stronger the covalent bond.
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why is the ci bond weakest and what's reactivity of haloalkanes
less energy required to break the bond.
iodoalkanes react the fastest then bromoalkanes
fluroroalkanes unreactive as way tm eenrgy needed to break C--F bond.
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general equation for hydrolysis of alkanes W water
CH3CH2CH2CH2X+H20---CH3CH2CH2CH2OH+H+X-
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how can the rate of hydrolysis be measured on each haloalkane
by carrying out reaction in presence of aqueous silver nitrate.As it takes place halide ions,X- , are produced which react w ag+(aq) ions to form precipitate of the silver halide.
ag+(aq) + X- ----AgX(s)(ppt of silver halide)
nucleophile is water,present in the aqueous silver nitrate.as haloalkanes are insoluble in water, reactions carried out in presence of ethanol solvent. this allows the water and haloalkane to mix n produce a single solution rather than 2 layers.
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the actual experiment practical of hydrolysis of alkanes
1)Set up three test tubes as follows:
Tube 1: Add 1 cm of ethanol and two drops of 1-chlorobutane
Tube 2: Add 1 cm of ethanol and two drops of 1-bromobutane
Tube 3: Add 1 cm of ethanol and two drops of 1-iodobutane
2)Stand the test tubes in a water bath at 60 °C.
3)Place a test tube containing 0.1 mol dm-3 silver nitrate in the water bath and allow all tubes to reach a constant temperature.
4)Add 1 cm of the silver nitrate quickly to each of the test tubes. Immediately start a stop-clock.
5) Observe the test tubes for 5 minutes and record the time taken for the precipitate to form.
Observation
1-chlorobutane=A white precipitate forms very slowly.
1-bromobutane=A cream precipitate forms slower than with
1-iodobutane but faster than with 1-chlorobutane.
1-iodobutane=A yellow precipitate forms rapidly.
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why is it important the test tubes are placed in a waterbacth at 60c at the same time
Your comparing rate so temp must be constant otherwise no fair comparison as temp would affect rate
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describe the observations of this experiment
compound w slowest reaction is the strongest carbon halogen bond.
1chlorobutane reacts slowest and the c--cl bond is he strongest
1-iodobutane reacts fastest and the C--1-I bond is the weakest
SOOOOO rate of hydrolysis increases as strength or carbon halogen bond decreases
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what else affects rate of hydrolysis between haloalkanes other than strength of carbon halogen bond
if its primary secondary or tertiary
tertiary haloalkane is hydrolysed fastest whilst primary hydrolysed slowest.because
primary haloalkane reacts by a one step mechanism whereas tertiary haloalkane reacts by a two step mechanism:
(in first step the carbon halogen bond of tertiary haloalkane breaks by heterolytic fission forming a tertiary carbocation and a halide ion.in the second step a hydroxide ions attacks the carbocation to form the organic product.)
increased rate can be explained by the inc stability of the tertiary carbocation compared to primary carbocation.
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why is a tertiary carbocation more stable than a primary carbocation
Alkyl groups reduce the charge on the carbocation by pushing e- towards the positively charged ion. The more R-groups directly attached to the positively charged C in the carbocation the more the + charge is reduced making the ion more stable.
A tertiary carbocation has 3 alkyl groups directly attached to the positive C atom but a primary carbocation has only 1 alkyl group.
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Draw the structures of primary secondary and tertiary bromoalkanes
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What are organohalogen compounds
Molecules that contain at least one halogen atom joined to a carbon chain
They’re used in many pesticides
But rarely found in nature as they not broken down naturally in environment so quite concerning
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What’s the ozone layer
Found at edge of stratosphere at a height that varies from 10-40Km above earths surface.
Tiny fraction of gases from this layer is ozone but enough to absorb most of the damaging Uv-B from the suns rays allowing only a small amount to reach earths surface
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Effect of uv-B radiation
The radiation most commonly linked to sunburn. It’s feared continued depletion of ozone layer w allow more UVB radiation to reach earths surface
=bad for living organisms=increased genetic damage =greater risk of skin cancer in humans
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What happens in the stratosphere
ozone is continually being formed and broken down by the action of (UV) radiation.
Initially very high energy UV breaks oxygen molecules into oxygen radicals,O:
02 → 20
A steady state is then set up involving O2 and the oxygen radicals in which ozone forms and then breaks down. In this steady state, the rate of formation of ozone is the same as the rate at which it is broken down:
02 + O = O3
Human activity, especially in the production and use of chlorofluorocarbons (CFCs), has upset this delicate equilibrium.
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What are cfcs used for
They were the most common compound used as refrigerants ,aerosol propellants n ac units. They’re stable cuz of strength of carbon- halogen bond within their molecules. Until it reaches stratosphere,here they break down forming chlorine radicals who h catalyse breakdown of ozone layer.
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How do CFCs deplete ozone layer
stability of CFCs, due to the strength of their carbon-halogen bonds, means CFCs have a long residence time in the troposphere. It may take them many years to reach the stratosphere.
Once in the stratosphere,UV radiation provides sufficient energy to break a carbon-halogen bond in CFCs by homolytic fission to form radicals. The C-Cl bond has the lowest bond enthalpy and so is the bond that breaks.
As radiation initiates the breakdown, this process is called photodissociation. The photodissociation of CF,Cl,2 is shown below.
CF, Cl2→ CF2Cl• + Cl•
The Cl radical formed, Cl•, is a very reactive intermediate. It can react with an ozone molecule, breaking down the ozone into oxygen.
This breakdown occurs by a two-step process:
propagation step 1
Cl•+O3–ClO•+O2
propagation step 2
ClO•+O—Cl•+O2
The overall equation is
O3+O—2O2
step 2 regenerates a Cl radical, which can attack and remove another molecule of ozone in propagation step 1. The two propagation steps repeat in a cycle over and over again in a chain reaction.
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Are CFCs responsible for all ozone depleting reactions
No
Other radicals catalyse breakdown of ozone. Nitrogen oxide radicals are formed naturally during lightning strikes and also as a result of aircraft travel in stratosphere
Nitrogen oxide causes breakdown of ozone by
Propagation 1:No•+O3–No2•+O2
Propagation2:NO2•+O—NO•+O2
Overall equation is O3+O—2O2
