KEY-Problem Set#3 - Problem Set#3 PDF

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Problem Set#3...

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C HM1321 C KEY – Practice Problem Set #3 - Alkanes 1. Show the structural formulas for all isomers of molecular formula C6H14. The formula C6H14 fits CnH2n+2, indicating that the possible isomers are all saturated alkanes (no rings or multiple bonds). There are 5 possible structural isomers:

2. Write the Newman projection formulas for 3-methylpentane, viewed along the C2-C3 bond. H H

CH2CH3

H

CH3

H

H CH2CH3

H H 60º

H 60º

CH CH3 3

CH3

H 3C

H CH3

anti-staggered

eclipsed

gauche-staggered

CH2CH3

60º

60º CH3

CH3 CH2CH3

H H

60º H CH3

H

CH2CH3

H

H CH3

eclipsed

gauche-staggered

H CH2CH3

H H 3C 60º H CH3

eclipsed

3. What are the axial and equatorial positions in cyclohexane? How many of each one does it have? H

H H

The 6 axial positions point above and below the plane of the cyclohexane chair, and are shown in blue.

H H H

H

H H H H

H

The 6 equatorial positions point roughly in the plane of the cyclohexane chair, and are shown in red.

4. Draw Newman projection diagrams for the chair and boat configurations of cyclohexane. H

H

H

CH2

H

H H

H

CH2

H H

H H

H

CH2 CH2

HH

HH

CHAIR

BOAT

5. How many isomers of dimethylcyclobutane can you draw?

1,1

cis-1,2

trans-1,2

cis-1,3

trans-1,3

6. Name the following molecules. OH

a.

Cl

b.

OH

trans-1,3-cyclohexadiol Br

Cl

cis-1,2-dichlorocyclohexane

Br

d. I

c. cis-1,3-dibromocyclohexane

trans-1,4-diiodocyclohexane

7. Draw the more stable conformer of trans-1-ethyl-2-methylcyclohexane. CH3 2

1

CH2CH3

I

flip

1 2

CH2CH3 CH3

both groups are equatorial MORE STABLE...