Using the templates provided, draw the four possible diastereomers of 1-bromo-2-methylcyclopentane. (You must add the methyl group at a carbon adjacent to the bromine with wedge or dashed wedge bond, as appropriate.)

diastereomer 1
(1R,2R)-1-bromo-2-methylcyclopentane

diastereomer 2
(1S,2R)-1-bromo-2-methylcyclopentane

diastereomer 3
$( 1 R , 2 S )$-1-bromo-2-methylcyclopentane

diastereomer 4
$( 1 S , 2 S )$-1-bromo-2-methylcyclopentane

Question

Using the templates provided, draw the four possible diastereomers of 1-bromo-2-methylcyclopentane. (You must add the methyl group at a carbon adjacent to the bromine with wedge or dashed wedge bond, as appropriate.)
 
diastereomer 1
(1R,2R)-1-bromo-2-methylcyclopentane

diastereomer 2
(1S,2R)-1-bromo-2-methylcyclopentane

diastereomer 3
$( 1 R , 2 S )$-1-bromo-2-methylcyclopentane

diastereomer 4
$( 1 S , 2 S )$-1-bromo-2-methylcyclopentane

Quizplus · Accepted Answer

The Answer is You first must realize that the R or S configuration of carbon 1 is changed by moving the methyl from one adjacent carbon to the other. Thus, we have:

You first must realize that the R or S configuration of carbon 1 is changed by moving the methyl from one adjacent carbon to the other. Thus, we have: This is equivalent to interchanging two groups-in this case, the ring bonds-to the asymmetric carbon. Next, pick a configuration for carbon-2 and see what it is. We'll pick the easiest one, with the methyl up. We simply switch the methyl and hydrogen positions at carbon 2 to give the other two stereoisomers. So, on your paper, the structures should be as follows. (You don't have to show the Hs, as they are assumed to have opposite stereochemistry to the Br or CH<sub>3</sub> on the same carbon.) diastereomer 1 ( 1 R , 2 R ) -1-bromo-2-methylcyclopentane diastereomer 2 (1S,2R)-1-bromo-2-methylcyclopentane diastereomer 3 ( 1 R , 2 S ) -1-bromo-2-methylcyclopentane diastereomer 4 ( 1 S , 2 S ) -1-bromo-2-methylcyclopentane

This is equivalent to interchanging two groups-in this case, the ring bonds-to the asymmetric carbon. Next, pick a configuration for carbon-2 and see what it is. We'll pick the easiest one, with the methyl up.

We simply switch the methyl and hydrogen positions at carbon 2 to give the other two stereoisomers.

So, on your paper, the structures should be as follows. (You don't have to show the Hs, as they are assumed to have opposite stereochemistry to the Br or CH₃ on the same carbon.)

diastereomer 1

( 1 R , 2 R )

-1-bromo-2-methylcyclopentane

diastereomer 2
(1S,2R)-1-bromo-2-methylcyclopentane

diastereomer 3

( 1 R , 2 S )

-1-bromo-2-methylcyclopentane

diastereomer 4

( 1 S , 2 S )

-1-bromo-2-methylcyclopentane

Using the Templates Provided, Draw the Four Possible Diastereomers of 1-Bromo-2-Methylcyclopentane