X = number of reactions in which an aromatic compound is formed. Find the value of (X - 4).
(a) $AlC l_{3}$ (b) $AlC l_{3}$
(c) $AlC l_{3}$ (d) $AlC l_{3}$
(e) $NaN H_{2}$ (f) $NaN H_{2}$
(g) $2K$ (h) 2Na
(i) $HBr$ (j) $HBr$
(k) $HBr$

Question

X = number of reactions in which an aromatic compound is formed. Find the value of (X - 4).

(a) structure $AlC l_{3}$ (b) $AlC l_{3}$

(c) structure $AlC l_{3}$ (d) $AlC l_{3}$

(e) structure $NaN H_{2}$ (f) $NaN H_{2}$

(g) structure $2K$ (h) 2Na

(i) structure $HBr$ (j) $HBr$

(k) structure $HBr$

TestHub · Accepted Answer

(a) The product is the cyclopropyl cation, with no π electrons in the ring : not aromatic. (b) The product is the cyclopropenyl cation (2π) : aromatic. (c) The product is the cyclopentadienyl cation (4π) : anti-aromatic. (d) The product is the tropylium cation (6π) : aromatic. (e) The product is the cyclopentadienyl anion (6π) : aromatic. (f) The product is the cycloheptatrienyl anion (8π) : not aromatic. (g) Two electrons are added to give the cyclooctatetraene dianion (10π, planar) : aromatic. (h) 2Na removes both Cl to give cyclobutadiene (4π) : anti-aromatic. (i) The product is the cyclopropenyl cation : aromatic. (j) Protonation of C = O gives the hydroxytropylium cation (6π) : aromatic. (k) Protonation of C = O gives the hydroxycyclopentadienyl cation (4π) : anti-aromatic. Aromatic products form in (b), (d), (e), (g), (i) and (j), so X = 6 and (X - 4) = 2.

Chemistry - GOC Question with Solution | TestHub

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