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Organic Flashcards

1
Q

Nomenclature 5 rules

A

1) count the number of carbons in the longest carbon chain which contains the functional group to give the stem

2) the main functional group of the molecule gives you the ending of the name

3) Number the carbon with the longest chain with the main functional group of priority with the lowest number. If there is more than one chain pick the one with the most side chains. Number go before the functional group.

4) Any side chains or less important chains are added as prefixes. They go in alphabetical order.

5) If there is more than one identical side chain or functional group use tri- di- or tetra- before the name

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2
Q

Homologous Series

A

-Alkanes
-Branched Alkanes
-Alkenes
-Halogenoalkanes (-bromo, -chloro, -iodo)
-Alcohol (-ol)
-Aldehydes (-al)
-Ketones (-one)
-Cycloalkenes (cyclo -ane)
-Carboxylic Acids (-oic acid)
-Nitrile (-anenitrile)

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3
Q

Priorities of functional group

A

1) carboxylic acids
2) esters
3) nitrile
4) aldehydes
5) ketones
6) alcohol
7) alkenes
8) halogenoalkanes
9) alkanes

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4
Q

Combustion of Alkanes

A

-burn in oxygen to form carbon dioxide and water
-give out heat
-large negative enthalpies
-more carbons are present the greater the heat output
-incomplete combustion produces carbon monoxide and soot and is more likely to occur in longer chain hydrocarbons as these need more oxygen to burn

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5
Q

Pollutants-

A

Carbon Monoxide -
-produced via incomplete combustion
-poisonous gas which is colourless and odourless

Nitrogen oxides-
-produced when there is enough energy for nitrogen and oxygen to combine in the air for example high temp and pressure
-may react with water vapour and oxygen to form nitric acid and acid rain and photochemical smog

Sulfur Dioxide-
-produced from sulfur impurities when burning fossil fuels
-can also form sulphuric acid causing acid rain

Carbon Particles-
-produced for incomplete combustion
-irritate asthma and cause cancer

Unburnt hydrocarbons-
-when not all fuel is burnt
-greenhouse gases and photochemical smog

Carbon Dioxide-
-produced when hydrocarbons burn
-greenhouse gas

Water Vapour-
-produced when hydrocarbons burn
-greenhouse gas

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6
Q

Flue Gas desulphurisation-

A

-Fuels burnt in power stations contain sulfur compounds meaning sulphur dioxide can be produced this can be removed using flue gas desulphurisation

1) slurry of calcium oxide and water is sprayed into the gas and forms calcium sulphite which can be further oxidised to from calcium sulphate known as gypsum
and is a salable product such as plaster

2) uses calcium carbonate

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7
Q

Catalytic converter-

A

Reduces output of pollutants in an exhaust gas mixture
-honeycomb structure made of ceramic metal coated with platinum and rhodium metal
-honeycomb provides a large surface area
-metals act as catalysts to react gases together to from less harmful gases

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8
Q

Structural Isomerism

A

-2 or more compounds have the same molecular formula but a different structural formula
-have different chemical and physical properties

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9
Q

Chain isomers

A

-differences in the arrangement of a hydrocarbon chain

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10
Q

Positional isomerism

A

-same functional group is attached to the carbon chain but at different parts

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11
Q

Functional group isomerism

A

-where 2 compounds have the same molecular formula but different functional groups

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12
Q

Stereoisomerism

A

-compounds which have the structural formula but atoms are arranged differently in space
-two types are E and Z
-occurs in alkenes

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13
Q

Why does EZ isomerism occur?

A

-c=c bonds contain both sigma and Pi bonds
-Pi bonds arise as a result of the overlap of 2p orbitals from both C atoms in the formation of the covalent bond
-overlap occurs above and below the C atoms preventing free rotations of the groups about the double bond
-only occurs if the groups bonded to each carbon in the double bond are different

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14
Q

How to identify is it is an E or Z isomer?

A

-if the higher priority groups on each carbon are on the same side of the carbon double bond it is a Z isomer
-if the higher priority groups are on different sides of the carbon double bonds it is an E isomer
-higher priority group is the group with the highest atomic number

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15
Q

Drawing EZ isomers

A

1) draw c=c bond and extend the longest chain described
2)number the carbons
3)add the functional groups to the carbons
4)ensure groups are in the correct place and then you can identify which type

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16
Q

Alkanes

A

-saturated hydrocarbon
-contain single c-c and c-h bonds

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17
Q

Properties of alkanes

A

-do not dissolve in water as they are non-polar and water molecules are held together by h-bonds and alkanes with VDW forces so they do not interact
-shorter chain alkanes have lower boiling points due to weaker VDW forces as less electrons are present
-branched chain alkanes have lower boiling points as they are not as closely packed together

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18
Q

Alkane bonds

A

-held together by sigma orbitals between c-c or c-h
-all have a tetrahedral shape so a bond angle of 109.5
-all molecules rotated about c-c bonds
-very flexible
-shorter chains are more volatile

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19
Q

Crude Oil

A

-fossil fuel made up of the breakdown of organic matter such as plants and animals
-non-renewable
-causes environmental issues when burnt

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20
Q

Fractional Distillation

A

-used to sperate different molecules for different uses
-column is cool at the top and has smaller shorter chain lengths with low boiling points and viscosity
-hot at the bottom with longer chains of higher boiling points
-vapours cool and condense and separated into fractions
-thick residue at the base is called tar or bitumen and is used for road surfacing

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21
Q

Cracking-

A

-splitting longer chain hydrocarbons (alkanes) into shorter and small alkanes and alkenes

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22
Q

Thermal Cracking

A

-Large temperature and pressure
-producing a high percentage of alkenes and some smaller alkanes and H2
-alkenes made for raw materials

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23
Q

Catalytic Cracking

A

-Large temperature and slight pressure and uses zeolite catalyst
-produces branched alkanes, benzene, cyclohexane and some H2
-branched alkanes used as more efficient fuels
-benzene used as raw material for plastics,drugs,explosives etc

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24
Q

Haloalkanes

A

-similar to alkanes but with one or more of the hydrogen atoms replaced by a halogen -can contain more than one type of halogen

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25
Types of haloalkane
Primary - haloalkane have 1 R group attached to the carbon linked to the halogen Secondary- haloalkane have 2 R group attached to the carbon linked to the halogen Tertiary - haloalkane have 3 R group attached to the carbon linked to the halogen
26
Physical Properties
-polar c-x bonds are not polar enough to be soluble -main intermolecular forces are VDW and dipole-dipole attraction -boiling points increase with chain length and down the halogen group -due to increased VDW forces between larger molecules and increased number of electrons and therefore larger vdw -branches of the main carbon chain lowers the melting point not as compact so vdws are weaker -higher boiling point than alkanes due to having higher mr and are more polar
27
Bond polarity in haloalkanes
-halogens are more electronegative than carbon so carbon bonded to the halogen has a partial positive charge - electro deficient -it can be attacked by reagents that are electron-rich nucleophiles -the more polar a bond the more reactive a haloalkane as the C atom has the highest possible positive charge and is most easily attracted by a nucleophile
28
Bond Enthalpies of haloalkanes
-the c-x bonds get weaker as you go down the group -fluorine is the smallest atom of the halogens so the shared electrons in the c-f bond are strongly attracted to the nucleus creating a strong bond -bond enthalpies let us predict that iodo- compounds are the most reactive because their bonds are weaker, experiments show evidence for this
29
Ozone
-a molecule made from O3 which decomposes to oxygen -important as it protects the earth from harmful exposure to UV rays -too many UV rays can lead to cancer as the radiation damages DNA causing mutations -too much ozone can lead to lung irritation and the degration of plastics at ground level
30
Chloroflurocarbons
-CFC are destroying the ozone layer -they are non-flammable and not very toxic so used as refrigerants, propellants, solvents and degreasing
31
How do CFCs destroy the ozone layer
-chlorine free radicals are formed as the c-cl bond breaks homolytically in the presence of UV and ozone molecules are then attacked -chlorine free radical is not destroyed and acts as a catalyst in the breakdown of ozone Chlorine radical + ozone -> Oxygen + Chlorine oxide free radical Chlorine oxide free radical + ozone -> oxygen and chlorine free radical
32
Free Radicals
When a covalent bond breaks and one electron goes to each atom that originally formed the bond. Fragments of the original molecule have an unpaired electron and are called free radicals which are extremely reactive
33
Forming free radicals - Heterolytic fission
-breaking a covalent bond in a way in which the more electronegative atom takes both electrons from the bond to from a negative and positive ion -negative ion can donate electrons and is called a nucleophile -positive ion can accept electrons and is known as an electrophile
34
Forming free radicals - Homolytic fission
-breaking a covalent bond in a way in which each atom takes an electron from the bond forming 2 free radicals -makes negative ions called nucleophiles
35
Formation of halogenoalkanes
-occurs when alkanes react with a halogen in presence of UV light -substitution reaction as halogen replaces a hydrogen -chain reaction due to free radical substituation
36
Formation of halogenoalkanes steps
1) Initiation 2) Propagation 3) Termination
37
Initiation
-homolytic fission occurs between a halogen molecule -UV light provides energy for this to occur -C-H bond is stronger so does not break -2 free halogen radicals are formed molecule -> 2 free radicals
38
Propagation
1) halogen free radical takes the H atom from the organic compound to form an acid and a organic free radical organic compound + radical -> acid + organic radical 2) organic radical is very reactive so reacts with halogen molecule producing another halogen radical and haloalkane to start chain reaction organic radical + halogen -> haloalkane + halogen radical
39
Termination
-where free radicals are removed -two free radicals reacting to form a compound with no unpaired electrons 1) two halogen radicals react to give a halogen 2) two organic radicals react to produce a alkane 3) a halogen radical and organic radical react to produce a haloalkane
40
Rules for mechanisms
1) curly arrows show movement of electrons 2) electrons are negative so arrow will move towards atom with a positive charge 3)if covalent bond is breaking arrow will originate at that bond 4)if covalent bond forms arrow starts off atom with the lone pair of electrons
41
Nucleophilic Substitution
Where a nucleophile replaces a halogen in a halogenoalkane
42
Conditions of the reaction-
-Heating under reflux, means heating with a condenser placed vertically in the flask to prevent loss of volatile substances from the mixture. - solvent is usually a 50/50 mixture of ethanol and water, because everything will dissolve in that -heat The halogenoalkane is insoluble in water. If you used water alone as the solvent, the halogenoalkane and the sodium hydroxide solution wouldn't mix and the reaction could only happen where the two layers met.
43
Nucleophilic substitution with OH-
-produces an alcohol -forms from aqueous NaOH
44
Nucleophilic substitution with CN-
-produces CN molecule -forms from KCN -extends the carbon chain
45
Nucleophilic substitution with NH3-
-forms from being in a sealed container and dissolved in ethanol -if NH3 is in excess it can act as a proton acceptor (base) and form a NH4+ ion and molecule as the final product
46
Elimination Reaction
-where an OH- ion acting as a base removes the halogen from the alkane forming an alkene, water and halogen molecule.
47
Elimination Reaction Conditions
-heat -a concentrated solution of sodium or potassium hydroxide -pure ethanol as the solvent
48
How does the solvent and temperature encourage a specific type of reaction?
water = substitution ethanol = elimination cold = substitution hot = elimination
49
How does the type of halogenoalkane affect what type of reaction occurs?
primary = mainly substitution secondary = both substitution and elimination tertiary = mainly elimination
50
How does a OH- ion behave in a substitution reaction?
the hydroxide ions are acting as nucleophiles. For example, one of the lone pairs on the oxygen can attack the slightly positive carbon. This leads on to the loss of the bromine as a bromide ion, and the -OH group becoming attached in its place.
51
How does an OH- ion behave in a elimination reaction?
Hydroxide ions have a very strong tendency to combine with hydrogen ions to make water - in other words, the OH- ion is a very strong base. In an elimination reaction, the hydroxide ion hits one of the hydrogen atoms in the CH3 group and pulls it off. This leads to a cascade of electron pair movements resulting in the formation of a carbon-carbon double bond, and the loss of the bromine as Br-.
52
What does IR spectroscopy measure?
radiation that is emitted or absorbed from a molecule as certain molecules absorb specific frequencies -causes vibrational energy changes in the molecule as bond stretching and bond bending occur which moves them up energy levels
53
Explain the peaks on the IR graph
-absorption peaks are due to bond stretching and are found higher than 1500 -lower than 1500 is due to movement of whole molecule and forms the finger print region
54
what are the key points when interpreting a IR graph
-strength of absorption depends on polarity of the bond, more polar bonds give a change in polarity as they vibrate and this causes a stronger vibration -c=o stronger than c=c -h-bonding between molecules can effect the width and position of absorptions of o-h bonds
55
56
Explain how some plastics are not biodegradable
Plastics containing alkanes are not biodegradable as as there strong non-polar bonds will not be attacked by biological agents such as enzymes
57
High vs low density polyethene
Low density- polymerising ethane at high temp and pressure via free radical mechanism producing chain branching making product flexible with low density High density- uses a zeigler catalyst resulting in less branching making melting point higher and structure more rigid
58
Explain mechanical recycling
Separate the different types of plastic then washed and ground into small pellets where they are ground up, melted and remoulded
59
Explain feedstock recycling
Plastics heated to temperature to break polymer bonds and produce monomers which are used to make new plastics however can only be done a number of time before chains become to short and it degrades the plastics properties
60

Chemistry (9 decks)

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