Aldehyde, Ketone,Carboxylic acid

similarity between Aldehyde, Ketone,Carboxylic acid

• carbonyl compund

Other carbonyl groups than Aldehyde, Ketone,Carboxylic acid

• Acyl halide

• esters

• amide

• acid anhydride

what is acyl group

R—C=O

acetone structure

structure of acetophenone

structure of benzophenone

which is the elctrophillc and nucleophillic centres in the carbonyl group

methods to prepare aldehydes and ketones

• oxidation of alcohol

• dehydrogenation of alcohol

• hydration of alkyne

• ozonolysis of alkenes

Oxidation of alcohol to obtain aldehydes and ketones

aka dehydrogentaion

H from O-H and from C-H is removed

alcohols on oxidation give aldehydes

aldehydes on oxidation give carboxylic acids

if a strong oxidising agent such as KmNO₄ is used then we get carboxylic acid directly from alcohols

obtaining aldehydes and ketones from alcohols through oxidation

Mild oxidising agents

PCC(pyridinium chlorochromate) for primary alcohol to aldehydes

CrO₃ (chromium anhydride) for sec alcohols to ketones

Why dont tertiary alcohols undergo oxidation?

We know that, Oxidation of alcohols takes place by removal of H form O-H and the alpha C

But in tertiary alcohols there is no H in the alpha carbon therefore they dont undergo oxidation

Dehydrogenation of alcohols

passing volatile vapours of alcohols through metals at a high temperature

dehydrogenation of:

• primary alcohol- aldehyde

• sec- ketone

• tertiary they get dehydrated and give alkene

ozonolysis of alkenes

Hydration of alkynes

(alkynes are immisible in water)

only ethyne can make aldehyde

othere akynes make ketone

only in the presence of 333K and H2SO4/HgSO₄

How to prepare only aldehydes

Aldehyde from acyl chloride (ROSENMUND REACTION)

Hydrogenated in the presence of a catalyst

Aldehydes from nitrile (RCN) STEPHEN REACTION

instead of SnCl₂ we can also use DIBAL-H( diisobyutylaluminium) for reduction

Difference between nitrile and cyanide

if CN is there in organc then called nitrile

else cyanide

Aldehyde from esters

How to prepare aromatic aldehydes

Aromatic aldehydes are prepared from aromatic hydrocarbons through OXIDATION

you get benzaldehyde from toulene in the presence of chromyl chloride

ETARD REACTION :

you get benzaldehyde from toulene in the presence of chromyl chloride

use of CHROMIC OXIDE(CrO₃)

In the presence of acetic anhydride

another method to get aromatic aldehydes from aromatic hydrocarbons

SIDE CHAIN CLORINATION AND HYDROLYSIS

THIS IS A COMMERCIAL WAY

preparation of benzaldehyde

GATTERMAN-KOCH REACTION

Preparation of ketones

Ketone from acyl chloride

Ketone from Nitrile

Ketone from benzene

Friedel crafts acylation

Properties of aldehyde and ketones

chck cw and book

are aldehydes or ketones more reactive in nucleophillic addition reaction?

aldehydes are more reactive in nucleophillic addition for the following reasons :

• steric hinderamce in ketones

• +I effect (give electrons) of alkyl groups on alpha carbon which reduce its partial postive, hence does not get affected by a nucleophile quickly

nucleophillic addition reaction of aldehydes and ketones

• rxn with hydrogen cyanide

• rxn with Hydrogen sulphite(NaHSO₃)

• with griganard reagent

• with alcohols

• with ammonia and derivatives

nucleophillic addition reaction of aldehydes and ketones with HCN( HYDROGEN CYANIDE)

reaction of nucleophillic addition with pure HCN is slow. how do you fasten it?

by adding a base

Nucleophillic addition of aldehydes and ketones with Hydrogen sulphite(NaHSO₃).

Is it a reversible reaction? if yes then how to reverse

Nucleophillic addition of aldehydes and ketone with R-Mg-X (Griganard reagent).

alcohol formed

Nucleophillic addition of aldehydes and ketone with alcohols and whats the special case

Nucleophillic addition of aldehydes and ketone with alcohols with ammonia and derivatives

learn reaction of aldehydes and ketones with ammonia and its derivatives whith diff substituents of Z

REDUCTIONS OF ALDEHYDE AND KETONES

• To alcohols

• to hydrocarbons (wolf and clemmensen)

reduction of aldehydes and ketones to alcohol

• reduced using reducing agents like (LiAlH₄) AND NaBH₄

• Or catalytic hydrogenation

reduction of aldehydes and ketones to hydrocarbons

Clemmensen reaction

Wolff-Kisher reduction

Oxidation of aldehydes and ketones to carboxylic acids

Oxidation of aldehydes and ketones takes place differently.

Oxidation of ketones

you get mixture of carboxylic acids

Oxidation of aldehydes and ketones by Tollens test

• can be used to find out if the carbonyl compound is aldehyde or a ketone

• if the reaction takes place it is aldehyde

Oxidation of aldehydes and ketones by Fehling test

• reaction takes place for aldehydes but not ketones

• aromatic aldehydes do not respond to fehlings test