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Topic: Impossible task?  (Read 1258 times)

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Offline Dillema103

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Impossible task?
« on: February 28, 2019, 11:21:09 PM »
I have a task in which I need to draw a structural formula of 5-ethyl-hexane but I am not sure if that is possible as adding ethyl to the 5th carbon would add 2 additional ones making it a heptane. Does an alkyl not count towards the carbon chain making this possible as CH3CH2CH2CH2CH(CH2CH3)CH3, if not am I correct in assuming that it is not possible to complete this task?

Offline AWK

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Re: Impossible task?
« Reply #1 on: March 01, 2019, 02:15:03 AM »
According to nomenclature rules, only one ethyl-hexane exists - namely 3-ethyl-hexane.
Even for monosubstituted ethyl-heptanes, only locants 3- or 4- are possible (Rule: The locants are assigned such that the principal functional group gets the lowest possible locant).
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Offline Dillema103

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Re: Impossible task?
« Reply #2 on: March 02, 2019, 10:06:25 AM »
According to nomenclature rules, only one ethyl-hexane exists - namely 3-ethyl-hexane.
Even for monosubstituted ethyl-heptanes, only locants 3- or 4- are possible (Rule: The locants are assigned such that the principal functional group gets the lowest possible locant).

Thanks for the answer. What would happen in a case where locants 2- 3- and 4- were all occupied? Would the ethyl go on the 5th locant then?

Offline AWK

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Re: Impossible task?
« Reply #3 on: March 02, 2019, 11:08:58 AM »
The first branch of carbon chain should have the lower locant - 2,4-dimethyl hexane (not 3,5-...), 3-ethyl-2,4-dimethyl hexane, 3-ethyl-2,5-dimethyl hexane, 3-ethyl-2,2,4-trimethyl hexane, 3-ethyl-2,4,5-trimethyl hexane.
4-Ethyl-2,2,3,3-tetramethyl hexane is the correct name.
Search for branched hydrocarbons nomenclature.
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Offline Dillema103

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Re: Impossible task?
« Reply #4 on: March 02, 2019, 12:13:18 PM »
Much appreaciated!

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