Question

An acid $A$ which is an important constituent of vinegar, on reaction with red $P$ and $Br _{2}$ gives a monobromoderivative $(B)$ which on reaction with $NH _{3}$ gives white solid $(C)$. However ethanal on reaction with a mixture of ammonium chloride and sodium cyanide undergoes Streacker synthesis to give a product which on acidic hydrolysis gives another high melting solid $(D)$. If $x$ and $y$ are the total number of optical isomers of $(C)$ and $(D)$ respectively while $z$ is the total number of dipeptides that $(C)$ and $(D)$ can form, then what is the value of $(x+3 y-z) ?$

Answer 1

Acid $(A)$ is ethanoic acid as it is an important constituent of vinegar.


Now, since $(C)$ has no chiral carbon, So, $x=0$
And $(D)$ has one asymmetric carbon, so $y=2$
And total number $(z)$ of dipeptides which can be made by $(C)$ and $(D)$ are
$gly-gly, ala - ala, gly - ala, ala - gly$
Hence, $z=4$
So, $x+3 y-z=0+3 \times 2-4=2$