Problem Set 3 key - homework 3 PDF

Preview

Summary

homework 3...

Description

Name:_________________Discussion TF: _____________ BU ID:___________Discussion section:_________ Homework #3 Fall 2019-Due Wednesday 9/25 by 5 pm in the boxes outside SCI 299 Please make sure the put your name, discussion TF and BU ID on the top of this page. This problem set must be printed out and answers directly written on the printout. 1) Draw both chair conformations of the six membered rings below and circle the lowest energy conformation. If they are equal in energy circle both structures. Draw out all of the H atoms on your chair structure and clearly indicate the directionality for all of the H and non-H substituents. H

CH3

a)

H

H

H

H

H H CH3

H

H

H3C H

H3C

CH3 H

H

CH3 CH3 CH3 CH3

CH3

b)

CH3 CH3

H3C CH3

c) HO

H

H

H

O

HO

OH

H

H

H H

H H OH

H H

O CH3

H

H

H

OH

Br

H

OH

OH HO

HO H

H

OH H

H H OH

H H

H

H

O

e)

Br

H

OH OH

H HO

OH

O

H

OH HO H

OH

H

H H H

H

H

H

H H

H

H

CH3 CH3 H CH3

H

H

H

H H3C

H

H

OH

HO

CH3 H3C

H CH3

H3C H

d)

H

H H

CH3 H

H

H Br

H CH3 H

H CH3

O OH

H

CH3 O

Name:_________________Discussion TF: _____________ BU ID:___________Discussion section:_________ 2) Cyclohexane A does not adopt a chair conformation, but instead is in a twist boat conformation, which is usually higher in energy than a chair conformation. Cyclohexane B adopts a regular chair conformation. Why does cyclohexane A prefer a twist boat conformation and cyclohexane B prefer a chair conformation?

3) Assign the stereochemical configuration of the alkenes (E, Z or N (not a stereocenter)) shown below.

4) Below is a molecule called Iejimalide B, which is a natural product. Assign the stereochemical configuration of all of the indicated alkenes (E, Z or N (not a stereocenter)) found in Iejimalide B.

E

E

E

E

E O

H3CO

O H3CO

N H

O

Z

E

H NH OH

E

E

O

iejimalide B...