Chapter 7-9 Homework Key, CH341

|1. |Give the major organic product of the reaction of 1-ethylcyclopentene with each of the following reagents. Show |[pic] |
| |stereochemistry when appropriate. | |

|a. D2 with a Pt catalyst. D’s add |b. H-Br |c. H2O with H2SO4 as a catalyst. |d. Cl2: the Cl’s add trans to the |
|cis | | |C=C. |
|[pic] |[pic] |[pic] |[pic] |

2a. Draw an arrow-pushing mechanism for the following reaction.

[pic]

[pic]

The methanol attacks from the back side of the cyclic bromonium ion, since the Br is blocking the front side from attack.

b. This is two additions of H-Cl to a pi-bond, one after the other.
[pic]

[pic]
[pic]

4. Give IUPAC names for the following structures

|a. |[pic] |b. |[pic] |
| | | |4-butyl-5-propylcycloheptene |
| |7-propylundec-2-yne | | |
|c. |[pic] |d. |[pic] |
| |(2Z,8Z)-2,8-dichloro-6-ethyldodeca-2,8-diene | | |
| | | |cyclonona-1,5-diyne |

4. The following products can be prepared from given starting material by a series of two or three reactions. What are the needed sequences of reactions?

| |Starting material |Product |
|a. |[pic] |
| |The alcohol can be dehydrated to the alkene, which can be converted to the dichloro compound with Cl2. |
|b. |[pic] [pic] |
| |To make two C=C’s we need to have two bromines on the ring, and do two dehydrohalogenation reactions. A convenient way to add to bromines to a ring is to |
| |add Br-Br to a C=C. Why did we not make a triple bond instead of two double bonds? |
|c. |[pic] |
| |First we use a really strong base to remove the alkyne hydrogen, and make a strong nucleophile, which we react with a primary alkyl halide with an SN2 |
| |reaction, to make the bigger alkyne. |