topic 17,1-4- further organic

Question 1

what is an arene

Answer 1

ring compounds in which there are delocalised electrons

Question 2

aromatic compounds

Answer 2

the bonding in a compound which has delocalized elctrons forming π bonding in a hydrocarbon ring

Question 3

aliphatic molecules

Answer 3

chains of carbon atoms with rings that are not aromatic

Question 4

benzene

Answer 4

arene
colourless liquid boiling point of 80 *c
C6H6
carcinogenic
more stable than expected
resonance hybrid

Question 5

hydrogenation of benzene

Answer 5

heat under pressure with a nickel catalyst
C6H6 + 3H2 –> C6H12
can form cyclohexane

Question 6

bromination of benzene

Answer 6

bromine
headed under reflux with a catalyst ( a halogen carrier)

Question 7

nitration of benzene

Answer 7

conc nitric and conc sulfuric acid
warm but not over 50*

Question 8

friedel crafts alkylation

Answer 8

adding an alkyl group
product is methylbenzene (toluene)
aluminum chloride and Lewis acid catalyst
if lewis acid need anhydrous conditions

Question 9

problems with kekule structure

Answer 9

1- should decolourise bromine water as has c-c double bond however it does not
2- should be 4 isomers however only 3 are known to exist
3-bond lenths should not all be the same
4- lower enthlapy change than expected

Question 10

freidel - crafts alkylation with chloromethane

Answer 10

products are an alkylbenzene methylbenzene and hydrogen chloride

Question 11

freidel - crafts acylation

Answer 11

products are keytone phenylethanone and hydrogen chloride

Question 12

mechanism for bromination

Answer 12

Question 13

mechanism for nitration

Answer 13

Question 14

mechanism for Alkylation

Answer 14

Question 15

mechanism for Acylation

Answer 15

Question 16

bromination of phenol

Answer 16

room temp no catalyst
bromine water discolored
white precipitate formed

Question 17

why does brominination happen more readily in phenols than benzene

Answer 17

in Phenol
Benzene requires catalyst of FeBr3
oxygen in OH group has a lone pair which can merge with the electrons in delocalised pi bond
electron density of ring is increased molecule is now more reactive towards electrophiles
bromine polarised as they approach
this breaks Br - Br bond
Br+ electrophile attacks the ring

Question 18

chiral

Answer 18

when a carbon centre is attached to 4 different groups so the mirror image cannot be superimposed onto itself

Question 19

enantiomer
lactic acid - CH3CH(OH)COOH

Answer 19

optical isomers if it has a chiral centre

Question 20

SN1

Answer 20

substitution
nucleophilic
unimolecular - 1 species in rds
can attack from either side so two enantiomers can be formed
product has no optical activity
generally tertiary halogenoalkanes
racemic mixture formed

Question 21

SN2

Answer 21

substitution
nucleophilic
can only attack from one side
bimolecular- 2 species in rds
arrangement inverted -inversion
so optical activity of product different
generally primary halogenoalkanes
only 1 enantomer formed

Question 22

nucleophilic addition to carbonyls mechanism

Answer 22

Question 23

carbonyl reaction with hydrogen cynanide

Answer 23

hydrogen attaches to oxygen atom of carbonyl group and a cyanide group attaching to the carbon atom of the carbonyl
planar compound so forms a racemic mixture ie no optical activity.

Question 24

condensation polymerisation

Answer 24

joining of two monemers with the elimination of a small molecule

Question 25

polyesters

Answer 25

polymers that have monomers bonded with an ester link

Question 26

polarimetry

Answer 26

use of a polarimeter to measure optical activity light passes through a polariser which converts unpolarised to polarised. then through sample tube containing substance. if optically activated plane will be rotated. analyser is rotated

Question 27

monochramatic light source

Answer 27

light of one colour or frequency

Question 28

racemic mixture

Answer 28

a mixture containing equal amounts of two enantiomers carbonation in triagonal planar around central carbon so equal prob of attack by nucleophile from each side

Question 29

properties of chains

Answer 29

increase chain length - increase boil temp - decrease solublility

Question 30

carboxylic acids reactions

Answer 30

reduction - to primary alchohols neutralisation - completely with aqueous alkali forms carboxylate salts halogenation - OH is replaced by halogen forms aceyl halogenides esterfacation- alcohol and acid catalyst forms ester

Question 31

acyl chlorides

Answer 31

RCOCl contain carbonyl group replaced the oh in cooh with cl

Question 32

acyl reaction with water

Answer 32

vigorous reaction form carboxylic acid and HCl gas

Question 33

acyl reaction with alcohols

Answer 33

form Esther and HCl gas

Question 34

acyl reaction with conc ammonia

Answer 34

ammonium chloride and HCl formed

Question 35

acyl reaction amines

Answer 35

substitued amide e.g N-substitued amide and HCl secondary amine form two alkyl groups

Question 36

esters

Answer 36

naming - -thyl -oate RCOOR double bonded O colourless liquids low melting and boiling insoluble in water smells of fruit

Question 37

hydrolysis of esters

Answer 37

opposite of esterification acidic- acid speed up as a catalyst alkaline - goes onto completion rather than equilibrium -produces carboxylate salt

Question 38

test for aldehydes and keytones

Answer 38

oxidation with fehlings , benedicts or tollens positive result aldehyde negative keytone fehlings + benedicts - blue > red tollens - colourless > silver

Question 39

esther and acyl chloride reactivity

Answer 39

acyl chlorides more reactive as more suseptable to attack from nucleophiles

Question 40

differences in esterfacation with oyl and carboxylic acid

Answer 40

irreversable - reversable HCl formed - H2O formed faster no acid catalyst needed - needed

Question 41

cyclicalcohol to cyclicalkene

Answer 41

elimination experiement phosphoric acid heat use distilation and seperating funell then dry

Question 42

amyl acetate

Answer 42

pentyl ethanoate

Question 42

formation of isoamyl acetate

Answer 42

3-methylbutan-1-ol

Question 42

hydrolsis of amyl acetate compare

Answer 42

2 methods aqeous acid or alkali s - both make same alcohol d -acid is reversible alkaline is irriversable -acid produce carboxylic acid alkaline produce carboxylate ion -acid catalyst alkaline reactant

Question 43

how can samples of enatiomers be distinguished

Answer 43

rotate plane polarised light in different directions

Question 44

no of optical isomers

Answer 44

number of chiral centres x2

Question 45

iodoform test

Answer 45

CH3CO feature react with I2 OH- to form a yellow precipitate triiodomethane - CHI3