JEE Main 2022 · 26 Jun · Shift 1 · Chemistry Q77

ChemistrySingle correct+4 / -1Question 77 of 90

Among the following structures, which will show the most stable enamine formation ?

(Where Me is $-\mathrm{CH_3}$ )

Enamine (A): N-C(Me)=CH-OMe, Me drawn on the left, the =CH-OMe branch on the right

Enamine (B): N-C(Me)=CH-OMe with the OMe chain extended away to the right

Enamine (C): N-C(Me)=CH-OMe with OMe trans to the ring nitrogen and cis to Me

Enamine (D): MeO-CH=C(Me)-N with OMe drawn up towards the ring

Answer and worked solution

Official answer: C

Same enamine, different geometry. All four are the enamine of a piperidine-2-carboxylic acid with $\mathrm{CH_3COCH_2OCH_3}$ , drawn differently.

Most stable. In (C) the bulky ring nitrogen and the OMe group are on opposite sides of the C=C, so steric strain is least. NTA's key gives (C).

(C)

Topics:Amines Geometrical isomerism

JEE Main 2022 · 26 Jun · Shift 1, Chemistry question 77