(a) Optically active compound `(A)` with a pleasant smell has a saponification equivalent `(S.E) = 186`. If shows the following reaction.
(i) `(A) overset(Br_2) underset(C Cl_4)rarr NO` reaction
(ii) `(A) underset(H_3 O^(oplus))rarr underset("Soluble in" NaOH) ((B) and (C))`
Both `(B)` and `( C)` are chiral.
(iii) `(C) overset(I_2 + overset(Ө)O H)rarr` Positive test
(iv) `(C) overset(Conc.) underset(H_2 SO_4)rarr (D)` (No diastereomers)
(v) `Ag` salt of `(B) overset (Br_2) rarr (+-) (E)`
(vi) `(C) overset(TsCl)rarr overset(NaBr)rarr (E) (Chiral)`
Identify `(A)` to `(E)`
(b) How do the structures of `(A)` to `(E)` change if
(i) `(D)` exists as diasteremers.
(ii) `(C)` gives negative iodoform test.

Explanation

(a) (i) `(A)` is an ester since esters have a pleasant smell.
(ii) `(A)` does not react with `Br_2|C Cl_4` rArr Saturated ester.

(iii) General formula of ester : `(RCOOR)`.
`(S.E = Mw = 186)`
Number of `C` atom `= (Mw -" Mass of 20 atoms")/(14)`
=`(186 - 32)/(14) = 11`
`( :' "Mass of" CH_2 = 14)`
Therefore, the molecular formula of ester is `C_11 H_22 O_2`.
(iv) Acid `(B)` must have one more `C` atom than alcohol `(C)` because `(B)` on Hunsdiecker reaction loses one `C` atom to give `(E).(E)` is also obtained from `(C)` with not change in `C` atom.
(v) Alcohol `( C)` of the type `(CH_(3)-underset(OH)underset(|)(CH)-R)` on dehydration with `conc. H_2 SO_4` gives alkene of the type (since it does not show diastereomers).
(vi) Alcohol `( C)` contains five `C` atoms, so acid `(B)` must contain six `C` atoms.
(vii) The structure of alcohol `(C)` must be `(CH_(3)-overset(**)underset(OH)underset(|)(CH)-overset(CH_(3))overset(|)(CH)-CH_(3))` and it is optically active.
(viii) Alcohol `( C) overset (TsCl + NaBr) rarr (E)`
It suggests that skeleton of `(B)` and `( C)` should be the same.
(ix) The structure of acid `(B)` and alcohol `(C)` should be of the type :

(x) Therefore, the structure of ester `(A)` would be :

Reactions :

(`TsCl` refers to p-tolulyl sulphonyl chloride, .
(b) (i) If `(D)` exists as diastereomer (i.e. geometrical isomers), then we have

(ii) If alcohol `(C)` is chiral and gives negative iodoform test, then `(C)` would be :
`(Ho-overset(1)(CH_(2))-underset(CH_(3))underset(|)overset(2)(CH)-overset(3)(CH_(2))-overset(4)(CH_(3)))`
Reactions :

Structure of ester (A) :