organic chem II

Question 1

oxidation of primary alcohol

Answer 1

reagent: potassium dichromate
distil: aldehyde
heat under reflux: ketone

Question 2

oxidation of secondary alcohol

Answer 2

reagent: potassium dichromate
ketone

Question 3

oxidation of aldehydes

Answer 3

Reaction: aldehyde to carboxylic acid
Reagent: potassium dichromate (VI) solution and
dilute sulfuric acid.
Conditions: heat under reflux

Question 4

what is the observation:

Answer 4

the orange dichromate ion
(Cr2O7
2-) reduces to the green Cr 3+

Question 5

test for presence of aldehyde groups

Answer 5

tollens reagent
fehlings solution

Question 6

tollens reagent

Answer 6

Reagent: Tollen’s Reagent formed by mixing
aqueous ammonia and silver nitrate. The
active substance is the complex ion of
[Ag(NH3
)2
]+
. Conditions: heat gently
Reaction: aldehydes only are oxidised by
Tollen’s reagent into a carboxylic acid and
the silver(I) ions are reduced to silver atoms
Observation: with aldehydes, a silver mirror forms
coating the inside of the test tube. Ketones
result in no change

Question 7

fehlings solution

Answer 7

Reagent: Fehling’s solution containing blue Cu 2+ ions.
Conditions: heat gently
Reaction: aldehydes only are oxidised by Fehling’s
Solution into a carboxylic acid and the copper ions
are reduced to copper(I) oxide . . Observation: Aldehydes :Blue Cu 2+ ions in solution
change to a red precipitate of Cu2O. Ketones do
not react.

Question 8

reduction of aldehydes

Answer 8

Reagents: LiAlH4
In dry ether
Conditions: Room temperature and pressure

primary alcohol

Question 9

reduction of ketones

Answer 9

Reagents: LiAlH4
In dry ether
Conditions: Room temperature and pressure

secondary alcohols

Question 10

addition reaction carbonyls to form hydroxynitriles

Answer 10

Reagent: HCN in presence of KCN
Conditions: Room temperature and pressure
Mechanism: nucleophilic addition

Question 11

iodoform test

Answer 11

Reagents: Iodine and sodium hydroxide
Conditions: warm very gently

Conditions: warm very gently
Only carbonyls with a methyl group next to
the C=O bond will do this reaction.

product: yellow crystalline
precipitate with an antiseptic smell

Question 12

2,4 DNP

Answer 12

tests for carbonyls

The
product is an orange precipitate, Take the melting
point of orange crystals product from 2,4-DNP. Compare melting point with known values in database

Question 13

Hydrolysis of Nitriles

Answer 13

Reaction: Nitrile  carboxylic acid
Reagent: dilute hydrochloric/ sulfuric acid.
Conditions: heat under reflux

Question 14

reduction of carboxylic acids

Answer 14

primary alcohol

Reagents: LiAlH4
In dry ether
Conditions: Room temperature and pressure

Question 15

reaction of carboxylic acid with PCL5

Answer 15

Reaction: carboxylic acid  acyl chloride
Reagent: PCl5 phosphorous(V)chloride
Conditions: room temp

observe misty fumes of HCl produced.

Question 16

esterification

Answer 16

Carboxylic acids react with alcohols, in the
presence of a strong H2SO4 catalyst, to form
esters and water.

Question 17

hydrolysis of esters

Answer 17

reagents: dilute acid (HCl)
conditions: heat under reflux

carboxylic acid and an alcohol are formed.

Question 18

acyl chloride with water

Answer 18

acyl chloride 
carboxylic acid
Reagent: water
Conditions: room temp

Question 19

acyl chloride with alcohol

Answer 19

Change in functional group: acyl chloride ester
Reagent: alcohol
Conditions: room temp.