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A Level Chemistry > Module 4 (chapter 11, 12 and 13) - organic chemistry > Flashcards

Module 4 (chapter 11, 12 and 13) - organic chemistry Flashcards

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1
Q

Hydrocarbon

A

A compound made of only hydrogen and carbon atoms

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2
Q

Saturated

A

Compounds with single carbon-carbon bonds only

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3
Q

Unsaturated

A

Compounds with the presence of multiple carbon-carbon bonds including double, triple and aromatic rings

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4
Q

Aromatic

A

A compound containing a benzene ring

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5
Q

Aliphatic

A

A compound containing carbon and hydrogen joined in straight chains, branched chains or non-aromatic rings

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6
Q

Alicyclic

A

An aliphatic compound arranged in non-aromatic rings with or without side chains

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7
Q

Homologous series

A

A series of organic compounds having the same functional group but with each successive member differing by CH2

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8
Q

Functional group

A

A group of atoms responsible for the characteristic reactions of a compound

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9
Q

Molecular formula

A

The number and type of atom of each element in a molecule

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10
Q

Empirical formula

A

The simplest whole number ratio of atoms of each element present in a compound

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11
Q

Structural formula

A

The minimal detail that shows the arrangement of atoms in a molecule
E.g. butane = CH3(CH2)2CH3

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12
Q

Displayed formula

A

The relative position of atoms in a molecule and the bonds between them

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13
Q

Skeletal formula

A

The simplified organic formula shown by removing hydrogen atoms from carbon chains leaving the carbon chain and functional group

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14
Q

General formula

A

The simplest algebraic formula of a member of a homologous series

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15
Q

Alkene

A

C=C (ene)

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16
Q

Alcohol

A

OH (ol)

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17
Q

Aldehyde

A

CHO
Double bonded O and single bonded H on the end of the group
(Al)

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18
Q

Ketone

A

C=O
(In the middle of a group)
(-one)

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19
Q

Carboxylic Acid

A

COOH
C double bonded to O and then single bonded to O and H
(-oic Acid)

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20
Q

Amine

A

NH2
C bonded to N and then N bonded to two hydrogens
(Amine)

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21
Q

Chloro/bromo/iodo alkane

A

Cl, Br, I

  • replaces a hydrogen
  • chloro, bromo, iodo before alkane
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22
Q

Structural isomer

A

Compounds with the same molecular formula but a different structural formula (e.g. but-1-ene and but-2-ene)

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23
Q

Benzene ring and how is it drawn?

A

Six carbons all joined in a cyclical structure
-extra electrons form delocalised rings around it as each carbon should form 4 bonds but only 3 are shown. This is shown by a centralised circle in the compound

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24
Q

Alkyl

A

A stem meaning not all atoms are connected in a single chain

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25
Q

How do you write the alkyl stems?

A

The number of carbons determines its name
E.g. 1 carbon is called methyl
-you write them in alphabetical order when ordering the alkyl stems

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26
Q

what happens to the trend in boiling points of hydrocarbons?

A

as hydrocarbon chains get longer there boiling point increases

  • this is because there are more points of contact and hence more longer dispersion forces
  • therefore more energy is required to overcome these forces increasing the boiling point
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27
Q

why do alkanes have low reactivity?

A
  • due to their high bond enthalpy
  • the very low polarity of the sigma bond as the electronegativity of carbon and hydrogen is thought to be so similar the bond is considered non-polar
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28
Q

what is a sigma bond?

A

the overlap of the orbitals directly between the bonding atoms

  • each overlapping orbital contains one electron so the sigma bond has two electrons shared between the bonding atoms
  • the sigma bond acts as an axes around which the atoms can rotate freely so these shapes can rotate an aren’t rigid
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29
Q

what is the effect of branching on boiling point?

A
  • increased branching decreases boiling point as there are fewer points of contact so fewer London dispersion forces hence less energy is needed to overcome them
  • branching also weakens molecules ability to tesselate reducing their attraction and intermolecular forces further
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30
Q

what is the shape of alkanes?

A

-each carbon atom is surrounded by four electron pairs in four sigma bonds forming tetrahedral structure

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31
Q

why are alkanes used for combustion?

A
  • all of them react with a plentiful supply of oxygen to produce carbon dioxide and water
  • don’t produce toxic products
  • easy to transport
  • readily available
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32
Q

general equation for balancing combustion of alkanes

A

CxHy + (x + y/4)O2 —- xCO2 + y/2 H2O

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33
Q

what is incomplete combustion?

A
  • happens when there is a limited supply of oxygen
  • this results in the hydrogen atoms in the alkane always being oxidised into water but combustion of the carbon may be incomplete
  • this forms carbon monoxide, water, and carbon particulates
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34
Q

what is bad about carbon monoxide?

A
  • colourless odourless tasteless gas which is highly toxic
  • it combines irreversibly with haemoglobin in the blood forming carbooxyhaemoglobin preventing oxygen being transported around the body
  • can lead to poisoning and death
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35
Q

what are stereoisomers?

A

compounds with the same structural and molecular formula but different arrangements of atoms in space
- this is due to a lack of rotation around the double bond

36
Q

how do you name E and Z isomers?

A

if the two highest priority groups are on the same side of the C=C double bond it is a Z isomer, if they are on different sides its an E isomer
-compounds have priority if they’re heavier (larger mass number)

37
Q

how do you name using Cis-trans notation?

A
  • this is a form of E/Z notation yet in this case one of the groups attached to each carbon atom must be the same
  • cis isomer is the Z isomer
  • trans isomer is the E isomer
38
Q

what are the CIP rules?

A

-in the system, the atoms attached to each carbon atom in a double bond are given priority based off their mass number

39
Q

what is the structure of alkenes?

A
  • unsaturated hydrocarbons
  • they contain at least one double carbon bond
  • general formula c2h2n
  • cyclic alkenes or alkenes with more than one double bond don’t obey this formula
40
Q

what is the nature of the alkene’s double bond?

A
  • four electrons on carbons outer shell
  • for each carbon atom of the double bond, three of the four electrons are used in sigma bonds and one is used in a pi bond (in a p orbital, one from each carbon atom of the double bond)
  • the pi electron density is concentrated above and below the nuclei of the bonding atoms
41
Q

what is the effect of the pi bond on the double bond?

A

it locks the two carbon atoms in place preventing rational movement around the bond
-this makes their geometry different to that of alkane

42
Q

what is the shape of alkenes?

A
  • they form a trigonal planar shape
  • there are three regions of electron density around each of the carbon atoms
  • three regions repel each other ad far apart as possible forming 120 degree bond angles
  • all of the atoms are in the same place
43
Q

what must a molecule have to satisfy E/s isomerism?

A
  • a C=C double bond

- different groups attached to each carbon atom of the double bond

44
Q

what are the bond enthalpies of carbon bonds?

A

c-c is 347kjmol-1 (sigma bond)
c=c is 612kjmol-1 (sigma bond and pi bond)
therefore bond enthalpy of pi bind is 265kjmol-1
it is weaker than the sigma bond so is broken more easily

45
Q

what is an addition reaction?

A

the addition of a small molecule across the double bond causing the pi bond to break and form new bonds

46
Q

what happens in the hydrogenation and halogenation of alkenes?

A
  • when reacted with hydrogen and passed over a nickel catalyst at 423K or reacted with halogens at room temperature an addition reaction happens
  • hydrogen or the halogen is added across the double bond
  • the more double bonds the more of this molecule needed to react
47
Q

how do you test for unsaturation?

A
  • add bromine water dropwise to a sample of an alkene
  • if carbon bond is present a bromine addition reaction happens across the double bond so sample turns from orange to colourless
  • if compound is saturated then no addition reaction happens so the solution isn’t decolourised
48
Q

what happens in the addition reactions of alkenes with hydrogen halides?

A
  • at room temperature they react to form haloalkenes

- there are two possible products

49
Q

what happens in the hydration of alkenes?

A
  • alcohols are formed when alkenes react with steam in the presence of a prosperous acid catalyst
  • steam is added across the double bond
  • there are two possible products
50
Q

what does the double bond in an alkene represent?

A
  • a region of high electron density due to the presence of the pi bond
  • this attracts electrophiles
51
Q

what is an electrophile?

A
  • an atom or group of atoms that is attracted to an electron rich centre and accepts an electron pair
  • it is usually a positive ion or a molecule containing an atom with a partial positive charge
52
Q

what are the mechanism steps for the electrophilic substitution reactions of alkenes?

A
  • the halogen atom in a hydrogen halide is more electronegative than hydrogen so it is polar (H is delta positive and halogen delta negative)
  • the electron pair in the pi bond is attracted to the electronegative halogen atom
  • a bond forms between the hydrogen atom of the H-Br molecule for example, and a carbon atom that was part of the double bond as the delta positive hydrogen is attracted to the electron rich double bond
  • the H-Br bond breaks by heterolytic fission with the electron pair going to the halogen atom
  • a bromide ion and a carbocation are formed
  • the halogen ion reacts with the carbocation to form the addition product
53
Q

how is a dipole induced in electrophilic reactions of alkenes with diatomic halogen molecules?

A
  • when bromine approaches an alkene the pi-bond interacts with the electrons in the Br-Br bond
  • this interaction causes polarisation of the bond with one end becoming delta positive and the other delta negative (induced dipole)
  • this happens because electrons repel each other so the pair of electrons in the Br-Br bond sit closer to the further atom
54
Q

after inducing a dipole, what is the mechanism for the electrophilic reactions of alkenes with diatomic halogen molecules?

A
  • the electron pairs in the pi bond is attracted to the delta positive end of the bromine bond causing the double bond to break
  • a covalent bond now forms between one of the carbon atoms and a bromine one
  • the Br-Br bond breaks by heterolytic fission with the electron pair going to the delta negative side of the Br bond
  • a bromine ion and carbocation form
  • the bromine ion reacts with the carbocation to form the addition product of the reaction
55
Q

what is a carbocation?

A

an organic ion in which a carbon atom has a positive charge

56
Q

what is Markovnikov’s rule?

A

when a hydrogen halide reacts with an unsymmetrical alkene the hydrogen becomes attached to the carbon with the most hydrogens attached to it already

57
Q

what are primary and secondary carbocations?

A
  • the primary carbocation is when the positive charge is on a carbon atom at the end of a chain
  • secondary carbocation is when the positive charge is on a carbon atom with two carbon chains attached
58
Q

which carbocations are the most stable?

A

tertiary carbocations are the most stale

primary carbocations are the least stable

59
Q

why are certain carbocations more stable?

A
  • the more methyl groups the greater the inductive effect
  • therefore the carbon atom with the most carbon chains has greatest inductive effect so is most stable and therefore is mist likely to form
60
Q

why are more alkyl groups more stable?

A
  • each alkyl group donates and pushes electrons towards the positive charge of the carbocation
  • the positive charge is spread over the alkyl groups so the more ally groups the more spread out charge is
  • this makes it more stable
61
Q

what yield of products are created in these addition reactions?

A
  • the intermediate carbocation formed is secondary
  • this means it is more stable as it has two inductive effects
  • this makes it more likely to form increasing the yield of that product
62
Q

what is the reaction of alkanes with halogens?

A

in the presence of sunlight alkanes react with halogens as the high energy UV radiation provides the initial energy for a reaction to take place

63
Q

what is fission?

A
  • the breaking of a covenant bond
  • homolytic = “ “ with one of the bonded electrons going to each atom
  • heterolytic = “ “ with both of the bonded electrons going to one of the atoms forming a cation and anion
64
Q

what is stage one of the substitution for the radical substitution of alkanes

A
  • initiation is when the covelant bond in a halogen molecule is broken homolytically
  • this forms two highly reactive halogen radicals
65
Q

what is stage two for the radical substitution of alkanes?

A
  • propagation when radicals attack the alkane
  • propagation tends to terminate when two radicals collide
  • first step = one of the halogen radicals steals one of the hydrogen atoms forming a carbon radical and a hydrogen halide
  • step 2= the carbon radical reacts with another halogen molecule to form a haloalkane and to regenerate a halogen radical
66
Q

what is stage three for the radical substitution of alkanes?

A
  • termination
  • two radicals collide and combine forming a molecule with all electron pairs
  • when two radicals react both are removed from the reaction mixture stopping the reaction
67
Q

what are the limitations of radical substitutions in organic synthesis?

A
  • further substitution happens and can continue until all hydrogen atoms have been substituted
  • this results in a mixture of products
  • it also creates substitution at different positions in carbon chains creating mixtures of mono substituted isomers
68
Q

what is a mechanism?

A

a sequence of steps showing the path taken by electrons in a reaction

69
Q

what is a monomer and polymer?

A

monomer= the small molecules which join together to make a polymer
polymer=long chain molecule that is made from the same repeating unit

70
Q

what is addition polymerisation?

A

process by which many unsaturated alkene molecules add on to a growing polymer chain at one time to form a very long saturated molecular chain
-they have high molecular mass

71
Q

how do you write polymers?

A
  • put repeating unit in square brackets with bonds coming outside of them
  • after the bracket place a letter n to represent large number of repeating units
  • naming them by putting monomer name in brackets with poly before it
72
Q

uses of poly(propene)

A
  • childrens’ toys
  • packing crates
  • guttering and window frames
73
Q

uses of poly(styrene)

A
  • packing material

- food trays and cups due to thermal insulating property

74
Q

uses of PTFE

A
  • used as coating for non stick frying pans
  • permeable membrane for clothes and shoes
  • cable insulation
75
Q

what is good and bad about recycling polymers?

A
  • conserves finite reserves like fossil fuels and decreases the amount sent to landfill
  • yet can only be recycled a finite number of times and when miseducating their properties are often rendered sometimes making it unusable
  • long process to sort them out, they’re washed dried and melted before being made into pellets that can be reused
76
Q

what is significant about recycling PVC?

A
  • its disposal is hazardous dent high chlorine content and range of additives so landfill isn’t sustainable
  • when burnt it also releases hydrogen chloride a corrosive gas and other pollutants like toxic dioxins
  • therefore recycling it involves using solvents to dissolve the polymer which is then recovered by precipitation from the solvent which can be used again
77
Q

what is good and bad about burning polymers for fuel?

A
  • some polymers hold a high stored energy value
  • they can be burnt to generate heat generating steam to turn a turbine and produce electricity
  • this reduced reliance on things like fossil fuels
  • yet produces harmful toxins through burning contributing to greenhouse effect
  • also energy needed to burn it may be expensive
78
Q

what is feedstock recycling?

A

describes the chemical and thermal processes that can reclaim monomers from waste polymers
-major bonus is that it is able to handle unsorted and unwashed polymers so is a quick snd simple process

79
Q

what are bioplastics?

A

plastics produced from a biological origin like starch

80
Q

what is good and bad about biodegradable polymers?

A
  • broken down by micro-organisms into water, carbon dioxide and biological compounds
  • they usually contain additives to alter the traditional structure of the polymer making them easier to break down
  • compostable polymers leave no visible toxic residues
  • they tend to be used in packaging, electronics and more fuel efficient transport vehicles
81
Q

what are photodegradable polymers?

A
  • oil based polymers
  • these contain bonds which are weakened by absorbing sunlight to start the degradation
  • light absorbing additives are also used
82
Q

what is a better alternative to burning plastics?

A

gasification
-process which melts plastics at very high temperatures in the near absence of oxygen
-this generates a synthetic gas used to fire turbines but with natural gas
pyrolysis
-plastics are shredded and melted at even lower temperatures and in the presence if even less oxygen breaking them into shorter chained hydrocarbons
-these can be refined and used as fuel for other chemical products

83
Q

drawbacks of biodegradable plastics?

A
  • don’t always readily decompose some need access to UV light
  • growing corn for starch uses up land that could be used to grow food perhaps leading to competition and shortages
  • oxydegradable plastics often just float on water as fragments as it is too cold to break them down
84
Q

what is a pi bond

A
  • formed by the sideways overlap of p orbitals

- forms the second and third bond between atoms

85
Q

ethyne

A

triple bond

CnH2n-2

A Level Chemistry (21 decks)

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