JEE Advanced 2017 · Paper 2 · Chemistry Q12

ChemistryMultiple correct+4 / -2Question 30 of 54

Among the following, the correct statement(s) is(are)

\ce{Al(CH3)3}

has the three-centre two-electron bonds in its dimeric structure

\ce{BH3}

has the three-centre two-electron bonds in its dimeric structure

\ce{AlCl3}

has the three-centre two-electron bonds in its dimeric structure

The Lewis acidity of

\ce{BCl3}

is greater than that of

\ce{AlCl3}

Answer and worked solution

Official answer: A, B, D

(A) $\ce{Al2(CH3)6}$ : each bridging $\ce{CH3}$ shares one sp³ orbital and 2 electrons between two Al atoms, a 3c-2e bond. True.
(B) $\ce{B2H6}$ has two B-H-B 3c-2e "banana" bonds. True.
(C) In $\ce{Al2Cl6}$ each bridging Cl donates a lone pair, giving 2c-2e dative bonds (3c-4e overall), not 3c-2e. False.
(D) B is smaller and its $\ce{BCl3}$ has an empty p orbital more strongly exposed, so it is the stronger Lewis acid. True.

(A), (B), (D)

JEE Advanced 2017 · Paper 2, Chemistry question 12