Organic Chemistry I Chem 334 - Fall 2009

Homework 9 Answers

Professor Carl C. Wamser

1. Give complete names for each of the following:

a)

(R),(E)-1-bromo-1-cyclopentylhex-4-en-2-yne

b)

(S),(E)-3-chloro-3,7,7-trimethyloct-4-en-1-yne

2. Write a complete mechanism for the addition of two equivalents of HBr to propyne. Show all intermediates, and explain whether or not Markovnikov's Rule applies to each addition.

Note that the first step is probably better described as an AdE3 mechanism (see text) rather than involving a vinyl cation. Nevertheless, Markovnikov's Rule still applies.

3. Write a synthetic sequence that shows how to make cis-5-methyl-2-hexene. Allowable starting materials are acetylene and any alkyl halide or alcohol that has four carbons or fewer. You may also use any necessary solvents or inorganic reagents.