Winter 2016 Quiz#3 Prep(pg43)

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Winter 2016 Quiz#3 Prep(pg43)

Postby 704578485 » Thu Mar 03, 2016 9:49 am

On pg 43 of the quiz workbook you are asked on question 2 to name CH3CH(CH3)CH(CH2CH3)C(CH3)3. I understand that the longest carbon chain contains 5 carbons. The answer given is 2,2,4-trimethyl-3ethyl pentane. I see how you get that if you identify the main carbon line as the 4 carbons not in parentheses plus a carbon from one of the methyl groups at the end parentheses. However, couldn't you also make the main chain the first 3 carbons not in parentheses plus the 2 carbons from the CH2CH3 in parentheses. Wouldn't this leave you with a pentane but with different substituent names than from the answer given?

Cindy Chen_2I
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Re: Winter 2016 Quiz#3 Prep(pg43)

Postby Cindy Chen_2I » Thu Mar 03, 2016 11:38 am

We would rather break the carbon chain down to more simpler substituents than one big substituent.
In the incorrect naming, you will end up with a tert-butyl as apposed to a ethyl and two methyl given in the correct answer.

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Re: Winter 2016 Quiz#3 Prep(pg43)

Postby Chem_Mod » Thu Mar 03, 2016 5:28 pm

When multiple chains are competing for selection to be the parent chain and they are all tied for length, then you should pick the chain that has the most things attached to it. Note that when numbered correctly, there are 4 sidechains. Any other way of numbering would result in either 2 or 3 sidechains.

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