Dibromopentane isomers

These two compounds are constitutional isomers (skeletal isomers), (b) The two dibromopentane stereoisomers are diastereomers. 

Any of several isomers of dibromopentane give mostly 2-pentyne on dehydrohalogenation with fused KOH at 200°C. In each case, the alkyne initially formed rearranges to the most stable isomer, 2-pentyne. 

Using 2,3-dibromopentane as an example, the following sequence explains how we can draw all of the possible isomers for a moleoule thaf confalns more fhan one chirality center. Remember that in the case of 2,3-dibromopentane we expect a maximum of four possible isomers beoause there are two chirality centers (2", where n is the number of chirality centers). 

Which isomer, 2,2-dibromopentane or 3,3-dibromopentane, would give the better yield of 2-pentyne using sodium amide as the base ... 

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