Organic Chemistry 2

Question 1

optical isomerism is a result of

Answer 1

chirality in molecules with a single chiral centre

Question 2

chiral carbon

Answer 2

• carbon atom bonded to four different groups or atom
• 3D molecule with no plane of symmetry
• non-superimposable on its mirror image

Question 3

what are optical isomers

Answer 3

non-superimposable mirror images

Question 4

optical activity

Answer 4

Rotates plane-polarised monochromatic light in opposite directions
-single enantiomer

Question 5

racemic mixture

Answer 5

an equal number of each enantiomer

Question 6

Simple substances which show optical isomerism exist as two isomers known as

Answer 6

enantiomers

Question 7

achiral

Answer 7

carbon that has a plane of symmetry

Question 8

aldehyde functional group

Answer 8

R-COH c=o with hydrogen

Question 9

ketone functional group

Answer 9

R-CO-R c=o

Question 10

name ending of an aldehyde

Answer 10

-al

Question 11

ketone name ending

Answer 11

-one

Question 12

intermolecular forces ketones and aldehydes can form

Answer 12

-london forces
-dipole-dipole, polar c=o bond
no hydrogen bonds:don’t have any hydrogen atoms attached directly to the oxygen

Question 13

aldehyde and ketone solubility in water

Answer 13

soluble, but falls with chain length

can form hydrogen bonds with water (slightly positive hydrogen)

Question 14

test for a carbonyl group

Answer 14

2,4-dinitrophenylhydrazine (Brady’s reagent)

room temperature yellow producing orange crystals

Question 15

oxidisation of carbonyl with Tollen’s reagent

Answer 15

Heat with ammoniacal silver nitrate
for aldehyde Silver mirror forms
for ketone no reaction occurs

Question 16

oxidisation of carbonyl with Fehling’s solution

Answer 16

heat

aldehyde Turns from a blue solution to form a red precipitate

Question 17

oxidisation of carbonyl with Dichromate solution

Answer 17

Heat with a mixture of potassium dichromate (vi) solution and sulphuric acid
Turns from an orange solution to a green solution

Question 18

Carboxylic acid functional group

Answer 18

C=O-OH

RCOOH

Question 19

Why may a substance have a chiral carbon but not be optically active

Answer 19

Equal amounts of the two enantiomers so the two rotations of plane-polarised light cancel out = racemic mixture

Question 20

How to get a pure sample or maximise the yield of an aldehyde

Answer 20

Distill off as it’s formed to prevent further oxidation

Question 21

Carbonyl compounds react with iodine

Answer 21

In presence of an alkali

Pale yellow precipitate of triiodomethane (iodoform) given by ketone or aldehyde with CH3-C=O-R