Aldhydes And Ketones(optical isomerism

Question 1

What does partial oxidation of primary alcohol form

Answer 1

It results an aldehyde forming

Question 2

What does oxidation of a secondary alcohol

Answer 2

Results in a forming a ketone

Question 3

What is the oxidizing agent used in the oxidation primary alcohol and secondary alcohol and aldehydes

Answer 3

Potassium dichromate in sulphuric acid (gentle warming needed)

Question 4

What happens to the potassium dichromate

Answer 4

The orange colour reduced to green

Question 5

What is the symbol for oxidation

Answer 5

[O]

Question 6

Give the simplified equations for oxidation reactions

Answer 6

R-CH2OH+[O]–R-CHO +H2O

Question 7

Give the oxidation reaction for secondary alcohol

Answer 7

R1-CH(OH)-R2+[O]–R1-CO-R2+ H2O

Question 8

When oxidised further what do aldehydes produce

Answer 8

Carboxylic acid

Question 9

What two tests can help distinguish between aldehydes and ketones

Answer 9

Tollens reagent

Feelings solution

Question 10

What occurs when aldehydes and ketones react with tollens reagent

Answer 10

Aldehydes- tollens reagent is reduced and a grey silver mirror forms (carboxylic acid formed)

Ketones-no reaction

Question 11

What happens when fehlings solution reacts with an aldehyde or ketone

Answer 11

Aldehydes- it’s reduced from the blue copper to red brick red precipitate on gentle warming

Ketone- no reaction

Question 12

What reducing agent is used to reduce aldehydes and ketones to alcohols

Answer 12

NaBH4 sodium tetrahydroborate

Question 13

What symbol shows reduction

Answer 13

[H]

2[H] in equation

Question 14

Give the simplified equation for the reduction of aldehyde

Answer 14

R-CHO + 2[H]-> R-CH2OH(primary alcohol)

Question 15

Give a simplified equation for reduction of ketone

Answer 15

R1-CO-R2 +2[H]->R1-CH(OH)-R2 (secondary alcohol)

Question 16

What reducing agent is used to reduce carboxylic acids

Answer 16

LiAlH4

Question 17

What reactions do carbonyls undergo

Answer 17

Nucleophilic addition

Question 18

What nucleophile undergoes nucleophillic addition with carbonyls in reduction

Answer 18

HCN

Question 19

Give the simplified equation for when HCN is reacted with carbonyls in reduction

Answer 19

R1-CO-R2 + HCN->R1-C(CN)(OH)-R2

Question 20

What is produced when carbonyls undergo reduction with HCN

Answer 20

Hydroxynitrile

Question 21

Write out equation for reduction by NaBH4 to make alcohols

Answer 21

R1-CO-R2+ 2[H]->R1-CH(OH)-R2

Question 22

What is chirality

Answer 22

When 4 different groups are attached to one carbon

Question 23

What are optical isomers (enantiomers)

Answer 23

They are two non superimposable mirror images

Question 24

How can optical isomers be distinguished

Answer 24

By passing plane polarised light through a liquid containing a chiral molecule

Question 25

What do chiral molecules do to plane polarised light

Answer 25

They cause it to rotate equally but in opposite directions One in clockwise rotation One in anti-clockwise rotation

Question 26

Define optically active

Answer 26

A substance which can rotate plane polarised light

Question 27

What is a racemic mixture

Answer 27

When optical isomers are found together in equal amounts

Question 28

What reactions do chiral substances undergo

Answer 28

Electrophillic addition Nucleophillic addition Nucleophillic substitution

Question 29

When a chiral substance is produced by an addition reaction what is it

Answer 29

It's a racemic mixture

Question 30

Why is a racemic mixture produced when by an addition reaction

Answer 30

As the attacking nucleophile or electrophile will attack the polar C-O bond planar molecule above and below in equal proportions

Question 31

What happens when a chiral substance undergoes nucleophillic substitutions

Answer 31

It only produces a single enantimor as the attacking species only attacks from one side

Question 32

Give the reagents involved in nucleophilic addition of carbonyl

Answer 32

KCN HCL Room temperature

Question 33

Why is HCn generated insitu and give the equation

Answer 33

As it's a very toxic gas KCN +HCl->HCN KCL