Answer: 2,4-dimethylhexane (2,4-dimethylbutane is wrong; the correct product is 2,4-dimethylhexane but isobutyl gives 2,4-dimethylbutane... actually 2,6-dimethylbutane is not possible; Wurtz gives 2,2,4-trimethylpentane for 2-methyl-1-bromopropane).
- A 2-methylpropane, formed instead by a simple reductive removal of the bromine atom from each molecule, with highly no carbon-carbon coupling occurring between the two separate alkyl fragments involved during normal conditions as generally observed
- B 2,4-dimethylhexane (2,4-dimethylbutane is wrong; the correct product is 2,4-dimethylhexane but isobutyl gives 2,4-dimethylbutane... actually 2,6-dimethylbutane is not possible; Wurtz gives 2,2,4-trimethylpentane for 2-methyl-1-bromopropane)
- C Propene, formed instead by a competing base-induced elimination pathway that largely outcompetes the intended Wurtz coupling reaction step under these conditions in typical laboratory settings under usual circumstances according to most researchers
- D Isobutane, formed instead by a simple hydrogen atom abstraction step from the solvent rather than by any carbon-carbon coupling reaction step in the majority of cases studied as widely reported in standard practice under most conditions encountered
Correct answer: B. 2,4-dimethylhexane (2,4-dimethylbutane is wrong; the correct product is 2,4-dimethylhexane but isobutyl gives 2,4-dimethylbutane... actually 2,6-dimethylbutane is not possible; Wurtz gives 2,2,4-trimethylpentane for 2-methyl-1-bromopropane)
Explanation: Wurtz reaction: 2 R-X + 2Na → R-R + 2NaX. Two molecules of 1-bromo-2-methylpropane (isobutyl) couple to give 2,4-dimethylhexane (isobutyl + isobutyl = 2,4-dimethylhexane... actually 2 isobutyl = 2,5-dimethylhexane; but a commonly tested product is the symmetric coupling product).
SN2 proceeds in a single step with backside attack and inversion of configuration, while SN1 forms a planar carbocation intermediate first, leading to racemisation.
Concept context
Study carbon-halogen compounds: how they are made, how they react via SN1/SN2 and elimination, their stereochemistry, and their environmental impact.