Test: JEE Main 35 Year PYQs- Aldehydes, Ketones & Carboxylic Acids - JEE MCQ

On vigrous oxidation with potassium permanganete, the aldehyde group is oxidized to acid.
The carbon carbon double bond is broken and both the carbons attached to double bond are oxidized to carboxylic groups.
(CH₃​)₂​C=CH−CH₂−CHO ---------->(Acidified potassium permanganate) ​(CH₃​)₂​COOH + CH₂​(COOH)₂​

2,4,6-trinitrophenol is also known as picric acid.

LiAlH₄ can reduce COOH group and not the double bond.

There is no reaction hence the resultant mixture contains CH₃ COOC₂H₅ + NaCl.

It is Clemmensen’s reduction

This reaction  is known as cannizzaro’s reaction. In this reaction benzaldehyde in presence of  50%. NaOH undergoes disproportionation  reaction and form one mol of Benzyl  alcohol (Red. product) and one mole of sod. benzoate (ox. product)

pK_a = –log K_a; HCOOH is the strongest acid and hence it has the highest K_a or lowest pK_a value.

NOTE : Addition of HCN to carbonyl compounds is nucleophilic addition reaction. The order of reactivity of carbonyl compounds is Aldehydes (smaller to higher) Ketones (smaller to higher), Then                    

HCHO > CH₃COCH₃ > Ph.COCH₃ > PhCOPh

NOTE : The lower reactivity of Ketones is due to presence of two alkyl group which shows +I effect.
The reactivity of Ketones decreases as the size of alkyl group increases.

The correct order of increasing acid strength

CF₃ . COOH > MeOCH₂COOH > CH₃COOH > (Me)₂CH.COOH

[NOTE : Electron withdrawing groups increase the acid strength and electron donating groups decrease the acid strength.]

Fruity smell is due to ester formation which is formed between ethanol and acid.

Phenol gives a violet colour with neutral ferric chloride solution whereas benzoic acid does not give this test.

In Cannizzaro’s reaction the compounds which do not contain a-hydrogen atoms undergo oxidation and reduction simultaneously i.e undergo disproportion ation and form one molecule of sodium salt of carboxylic acid as oxidation product and one molecule of alcohol as reduction product.

The electron withdrawing (–I) group – Cl withdraws electrons from O – H bond and thus helps the cleavage of the O – H bond releasing hydrogen as H+.

Both for maldeh yde an d a cetaldeh yde give silver mirror with Tollen’s reagent.

Iodoform is given by 
1) methyl ketones R-CO-CH₃
2) alcohols of the type R-CH(OH)CH₃
where R can be hydrogen also

Aldehydes and ketones canbereduced to hydrocarbons by the action (i) of amalgamated zinc and concentrated hydrochloric acid (Clemmensen reduction), or (b) of hydrazine (NH₂NH₂) and a strong base like NaOH, KOH or potassium tert-butoxide in a high-boiling alcohol like ethylene glycol or triethylene glycol (Wolf-Kishner reduction)

An excellent reagent for oxidation of 1° alcohols to aldehydes is PCC.