What is the major product formed when 2-methyl-2-hexene reacts with HCl?

Question

I got this question wrong on an assignment because I put 2-chloro-2-methyl-2-hexene and the right answer was 2-chloro-2-methylhexene. Just curious as to why you don't include a 2 in between methyl and hexene on the product?

I knew that leaving out the 2 makes them two different chemicals but my question is how do you know when to show where the double bond is by using the correct number..

Answer 1

2-methyl-2-hexene + HCl --> 2-chloro-2-methylhexane

In the first step of hydrochlorination, the partially positive end of the H-Cl molecule is attracted to the electron-rich double bond, where protonation of carbon-1 of the double bond occurs. Subsequently, the more stable tertiary carbon cation is formed (carbon-2). The negatively charged chloride is the nucleophile that donates two electrons in the form of a covalent bond to the positively charged carbon cation, resulting in the formation of an alkyl halide (2-chloro-2-methylhexane) as major product.

Since the product is alkane (2-chloro-2-methylhexane), it is not 2-chloro-2-methyl-2-hexene. We don't have to put "2" before an alkane as in hexane. If we put 2-before hexene (i.e. 2-hexene), it means the double is between carbon-2 and carbon-3 (CH3CH=CHCH2CH2CH3). Another way to write it is hex-2-ene.

Answer 2

You have typed the "correct" answer wrongly. When alkenes undergo addition reactions, they change from "enes" to "anes", and the correct answer is 2-chloro-2-methylhexane.

Answer 3

Because those are two different chemicals.....