Naming an Alkyne

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Dianna Grigorian 1C
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Naming an Alkyne

Postby Dianna Grigorian 1C » Thu Mar 02, 2017 8:54 pm

In the textbook on page 19, an example is given of naming an alkyne with the formula (CH3)2CHC --- CH. How do we know that the longest carbon-carbon chain has four bonds and should be butyne rather than a chain of 5 carbons?

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Re: Naming an Alkyne

Postby Jamie_Lin_3I » Fri Mar 03, 2017 12:40 pm

I would suggest drawing the structure out with a chain of 4 carbons and a chain of 5 carbons. You will notice that for the chain of 5 carbons, the structure doesn't quite work out. There are 2 CH3. If you use the 5 carbon chain, you can only place the 2 groups of CH3 at the ends of the structure. If this is the case, you cannot place the triple bond anywhere because the rest of the carbons have 2 bonds already.
If you try with the 4 carbon chain however, you could use one CH3 group as a substituent and you can place the triple bond on the end.

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