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A Level Chem - OCR > Organic > Flashcards

Organic Flashcards

1
Q

functional group of alkenes

A

CnH2n

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2
Q

what does aliphatic mean

A

carbon atoms joined together in unbranched or branched chains, or non aromatic rings

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3
Q

what does aromatic mean

A

some/all carbon atoms are found in a benzene ring

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4
Q

what does alicyclic mean

A

carbon atoms are found in ring structures, with or without branches

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5
Q

definition of structural isomers

A

same molecular structure but different structural formula

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6
Q

definition of stereoisomers

A

same molecular and structural formula but a different arrangement of atoms in space

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7
Q

what do curly arrows stand for

A

movement of an electron pair

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8
Q

what is homolytic fission

A

when the covalent bond breaks, each bonded atoms takes one of the shared pair of electrons

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9
Q

what is heterolytic fission

A

when a covalent bond breaks, one of the bonded atoms takes both of the electrons from the bond

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10
Q

addition reaction

A

a molecule is added to the unsaturated alkene, breaking double bond

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11
Q

substitution reaction

A

an atom/group of atoms is replaced by a different atom or group of atoms

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12
Q

elimination reaction

A

the removal of a small molecule from a larger one - usually water

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13
Q

properties of alkanes

A

saturated hydrocarbons
has sigma bonds
tetrahedral shape

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14
Q

what happens to bp when chain length of alkanes increases

A

it increases as there is a larger surface area of contact between molecules so the London forces are stronger - more energy is required to overcome

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15
Q

what is the effect of branching on boiling point of alkanes

A

it decreases bp as there are fewer surface points of contact between molecules, London forces are weaker - less energy required to overcome them

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16
Q

why are alkenes relatively not highly reactive

A

the C-C and C-H bonds sigma bonds are strong
the C-C bonds are non polar
the electronegativity of Carbon and hydrogen is so similar that the C-H bond can be considered non-polar

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17
Q

what are the details of an alkene reaction with halogen

A
  • Needs UV light
    CH4 + Br2 -> Ch3Br + HBr
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18
Q

What is the mechanism for the bromination of alkenes

A

radical substitution

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19
Q

what are the steps to radical substitution withh examples

A
  1. Initiation - the bromine bond is broken by homolytic fission
    Br-Br -> Br* + Br*
  2. Propagation
    a) CH4 + Br* -> *CH3 + HBr
    b) CH3 + Br2 -> CH3Br + Br
  3. Termination - when 2 radicals collide o form a molecule
    *CH3 + *CH3 -> C2H6
    *Br + *Br -> Br2
    *CH3 + *Br -> CH3Br
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20
Q

what are the limitations of radical substitution

A

further substitution can occur until all hydrogen atoms have been substituted

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21
Q

what are the properties of a double bond
C=C

A
  • a sigma bond
  • sigma locked in place by the pi bond
  • pi bond is the overlap of 2 p orbitals above and below the plane of the carbon atoms
22
Q

what is the shape around the double bond

A

trigonal planar as
- 3 bonding pairs of electrons around each carbon atom
- 3 pairs repel each other as far apart as possible so the bond angle around each carbon atom is the same
- all atoms are on the same plane

23
Q

why and when does E/Z isomerism arise

A

because rotation around the double C=C bond is restricted and the group attached to each carbon atom are therefore fixed

it occurs when there is a C=C bond and there are different groups attached to each carbon atom of the double bond

24
Q

what is cis-trans isomerism

A

Zis is on ze zame zide!!

25
Q

what are the Cahn-Ingold-Prelog rules

A

if the groups of higher priority are in the same side of the double bond, it is a Z isomer
if the groups of higher priority are on diagonal sides, it is an E isomer

26
Q

which is more reactive alkenes or alkanes and why?

A

Alkenes because of the presence of the pi bond
pi bond is more electron dense and the electrons are more exposed than in the sigma bond

27
Q

when do alkenes undergo addition reactions

A
  • hydrogen in presence if a nickel catalyst
  • halogens
  • hydrogen halids
  • steam in the presence of an acid catalyst
28
Q

what is formed when alkenes react with steam and with what catalyst

A

alcohols when there is a phosphoric acid catalyst
steam adds across the double bond

29
Q

what is the mechanism of an addition reaction in alkenes

A

electrophilic addition

30
Q

what is an electeophile

A

an electron pair acceptor
an atom/group of atoms that is attracted to an electron-rich centre and accepts and electron pair
is usually a positive ion or a molecule containing a partial positive charge

31
Q

Mechanism for electrophilic addition reaction of But-2-ene with hydrogen bromide

A
  1. bromide is more electronegative than hydrogen, so HBr is polar and has a dipole
  2. the electron pair in the pi bind is attracted to partially +ve H atom - double bind breaks
  3. bond forms between H atoms of the H-Be molecule and a C atom that was part of the double bond
  4. the H-Br bond breaks by heterolytic fission, with the e- pair going to the Br atom
  5. a bromide ion (Br-) is made and a carbocation formed
  6. the Br- reacts with carbocation to form addition product
32
Q

what examples of disposing of waste polymers

A

recycling
PVC recycling
using them as fuel
feedstock recycling

33
Q

what are the details of PVC Recycling

A

hazardous due to high chlorine content and range of additive
when PVC. is burnt, it releases HCl and toxic dioxins

Now, solvents dissolve the polymer and the PVC is recovered by precipitation if the solvent

34
Q

what is feedstock recycling

A

the chemical and thermal processes that can reclaim monomers, gases or oil from waste polymers

35
Q

how do biodegradable polymers break down

A

by microorganisms into water, carbon dioxide and biological compounds
polymers are usually made from starch or cellulose
leave no toxic residue

36
Q

what is a primary alcohol

A

when. the -OH group is attached to a carbon atom that is attached to two hydrogen atoms and one alkyl group
methanol is the exception

37
Q

what is a secondary alcohol

A

when the -OH group is attached to a carbon atom that is attached to one H atom and 2 all groups

38
Q

what is a tertiary alcohol

A

when the -OH group is attached to a carbon atom that is attached to no H atoms and 3 alkyl groups

39
Q

what are secondary alcohol oxidised to

A

ketones

40
Q

is it possible to oxidise ketones using acidified dichromate

A

no

41
Q

what is is produced when
a primary alcohol is heated strongly under reflux with acidified dichromate

a primary alcohol is gently heated and distilled over as formed

A

carboxylic acid
aldehyde

42
Q

how can you test if you have made an aldehyde

A

using acidified dichromate
will then from orange to green

43
Q

how do you produce an allen’s from an alcohol

A

heat the alcohol under reflux in the presence ing an acid catalyst - concentrate sulfuric acid/concentrated phosphoric acid

44
Q

what are examples of nucleophiles

A

OH-
H2O
NH3

45
Q

what are the steps to hydrolysis of a haloalkane where the halogen is replaced by an -OH group

A
  1. OH- approaches carbon atom attached to halogen, on the other side of the C atom to where the bond is
  2. direction of attack minimises repulsion between nucleophile and the halogen atom
  3. lone pair of electrons in the OH- ion is attracted and donated to the partially +ve carbon atom
  4. new bond is formed between the O atom of OH- and the C atom
  5. carbon-halogen bond breaks by heterolytic fission
  6. alcohol and halide ion formed
46
Q

how can haloalkanes be converted to alcohols

A

using aqueous sodium hydroxide and heated under reflux - to obtain a good yield

47
Q

what is the order of strength of the carbon-halogen bonds

A

strongest
C-F
C-Cl
C-Br
C-I
Weakest

48
Q

what can we predict from the carbon-halogen bind enthalpy

A

iodoalkanes react faster than bromoalkanes
bromoalkanes react fast than chloroalkanes
fluoroalkanes are interactive as a large quantity of energy is required to break the C-F bond

49
Q

what is the general equation for hydrolysis of primary haloalkanes

A

CH3CH2CH2CH2X + H2O -> CH3CH2CH2CH2OH + H+ + X-

50
Q

how can you measure the rate of hydrolysis of primary haloalkane

A

Using aqueous silver nitrate

Ag+ (aq) + C- (aq) -> AgX(s) precipitate of silver halide

51
Q

what can you observe with the precipitate in hydrolysis of primary haloalkanes
1. 1-chlorobutane
2. 1-bromobutane
3. 1-iodobutane

A
  1. a white precipitate that forms very slowly
  2. a cream precipitate that forms slower than 1-iodo but faster than 1-chloro
  3. a yellow precipitate that forms rapidly

A Level Chem - OCR (4 decks)

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