Carbonyls

Question 1

C=O bond reactivity:-

Answer 1

C=O is polar as O is much more electronegative. Don’t react w/ electrophiles, but can be attacked by nucleophiles because carbon is positive.

Question 2

Carbonyl group:-

Answer 2

C=O

Question 3

Carbonyl intermolecular forces:-

Answer 3

Stronger than alkanes/alkenes as dipole enables permanent dipole-dipole forces rather than van der waal’s forces.

Question 4

Melting/boiling point:-

Answer 4

Lower as not all hydrogen bonding like in alkenes/anes.

Question 5

Reaction w/ 2,4-dinitrophenylhydrazine:-

Answer 5

Aldehyde/ketone gives yellow/orange precipitate. Can be used to id. Recrystallising and heating to find melting point can be used to find specific compound.

Question 6

Tollens’ reagent:-

Answer 6

Can also oxidise aldehyde to carboxylic acid. Can be used as test. Heat in water bath. Silver ions will be reduced to metallic silver, coat test tube w/ ‘silver mirror’

Question 7

Forming alcohol from carbonyl:- (nucleophilic addition)

Answer 7

Add NABH4. Source of H- (hydride ions). Attacks C double bonded to O. Curly arrow from double bond to O. Negative O takes H from H2O which = solvent to complete reaction. Arrow from lone pair on O to H. Curly arrow from bond in H2O to OH part not attached.

Question 8

Hydroxynitrile:-

Answer 8

Alkane w/ OH group and CN groups.

Question 9

Nitrile group:-

Answer 9

CN group.

Question 10

Hyrdroxynitrile formation:-

Answer 10

HCN used on carbonyl. Dissociated into H+ and CN-. CN- = nucleophile, attacks C and is bonded. Usual H occurs with O-, forms OH group. Uses H+ from another HCN.

Question 11

HCN acidity:-

Answer 11

Weak acid, only slightly dissociates and is a weak nucleophile = slow reaction.