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chemistry > topic 17 > Flashcards

topic 17 Flashcards

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1
Q

what is a chiral centre

A

a carbon atom with four different groups bonded to it so the molecule has no line of symmetry`

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2
Q

what is optical isomerism

A

a type of stereo isomerism chiral carbon atoms with non super imposable mirror images of each other

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3
Q

how are chiral centres indicated

A

with an asterisk

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4
Q

what are two different optical isomers called

A

enantiomers

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5
Q

how do enantiomers differ from eachother?

A

they rotate the plane of polarised light

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6
Q

what is a racemic mixture?

A

this is two enantiomers that exist in equal amounts( equimolar)

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7
Q

how do enentiomers of the same molecule differ

A

they rotate light by the same degree in opposite directions

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8
Q

what happens to light in the presence of a racemate

A

the plane of polarised light remains the same as the polarisation rotation is cancelled out

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9
Q

what are the two ways that nucleophillic substitution can occur

A

the negative charge can leave the chiral carbon first so that the nucleophile can attack from any direction .

the nucleophile could attack at the same time as the negative charge leaves so that it can only attack from one direction.

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10
Q

what is a carbonyl compound

A

a organic compouds containing a C=O group.and the functional group of -CO

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11
Q

what are the most common carbonyl groups

A

aldehydes and ketones

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12
Q

how are aldehydes produced

A

via the oxidation and distillation of primary alcohols

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13
Q

what do aldehydes react with to form carboxyllic acids

A

potassium dichromate

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14
Q

how are ketones formed

A

through the oxidisation and distillation of secondary alcohols

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15
Q

whats the main difference between aldehydes and ketones?

A

the positioning of the CO group

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16
Q

what is the positioning of the CO group on aldehydes

A

it is always on the end of an organic group and ends in -al

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17
Q

how many of each atom is there in the atom proponal

A

3 carbons, 6 hydrogens. and one oxygen atom.

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18
Q

what is tollens reagent used for

A

to distinguish between aldehydes and ketones

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19
Q

why is tollens reagent heated in a water bath and not under a flame

A

this is a safety precaution because aldehydes and ketones are very flammable

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20
Q

how do we test for aldehydes and ketones?

A

acidified potassium dichromate (K2Cr2O7)

21
Q

what does potasssium dichromate show for the presence of aldehydes and ketones

A

it oxidises aldehydes. aldehydes turn from orange to green

no observations for ketones

22
Q

what functinal group does carboxyll have

A

-COOH

23
Q

what bonds do carboxyllic acids have

A

C=O(carbonyl group) bond and a -OH bond (a

24
Q

whats the general formula for aldehydes?

A

RCHO

25
Q

how are carboxylic acids formed from aldehydes

A

they are oxidised in the presence of acidified potassium dichromate (VI)

26
Q

what is the general formula for ketones

A

RCOR

C=O

27
Q

where is the carbonyl group on ketones

A

in between two hydrocarbon groups

28
Q

what alcohols can be oxidised

A

primary and secondary

29
Q

what happens when primary alcohols are heated in the presence of acidified potassium dichromate

A

an aldehyde is formed

30
Q

what happens when secondary alcohols are oxidises in the presence of K2Cr2O7

A

ketones are formed

31
Q

what is potassium dichromate used as and why

A

an oxidising agent because it is reduced in the reaction

32
Q

what will be observed when a tertiary alcohol reacts with potassium dichromate

A

no colour change is observed

33
Q

how can oxidation reactions to form carbonyl compounds from alcohols be reversed

A

they can be reversed through reduction reactions using lithium tetrehydridoaluminate in a dry ether

34
Q

why is the reduction reaction carried out in a dry ether

A

because lithium aluminium hydride reacts violently with water

35
Q

what is an arene

A

an aromatic compound that contains a benzene ring

36
Q

do arene have low or high boiling points and why

A

low boiling points because they are non polar and cant be dissolved in water

37
Q

do arenes have low or high melting points and why

A

high because of the high stability of the delocalised benzene ring

38
Q

how are the pi bonds in benzene formed

A

there is a delocalised outer electron in the p-orbital in each carbon going into the centre to form an overlapping ring

39
Q

why doesnt benzene undergo electrophillic addition

A

this would mean that the stable ring of electrons would be broken so instead electrophillic substitution occurs.

40
Q

what is halogenation

A

an electrophillic substitution reaction where benzene reacts with a halogens in the presence of a catalyst

41
Q

what is an example of a catalyst for halogenation reactions

A

FeBr3 iron(III) bromide

42
Q

what functional group is linked with carboxyllic acids

A

-COOH

43
Q

what is the general formula for grignards reagent and what is each letter

A

RMgX
R- alkyl group
Mg-magnesium
X-halogen

44
Q

what is an alkyl group example

A

methyl ethyl

45
Q

what is an amine

A

when an alkyl group replaces a hydrogen on ammonia

46
Q

what is the purpose of grignards reagent

A

to lengthen the carbon chain

47
Q

how do you distinguish between the classification of amine i.e primary secondary or tertiary

A

primary is only one alkyl group
secondary is two alkyl groups
tertiary is two alkyl groups that have displaced the hydrogen in ammonia

48
Q

what is formed when grignards reagent is reacted with carbon dioxide and hydrolysed

A

a carboxylic acid

49
Q

what is formed when grignards reagent is reacted with a carbonyl compound and hydrolysed?

A

an alcohol

chemistry (11 decks)

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