Organic Formulation Theory: Alkynes

Hydrocarbons with triple bonds, Acetylenes or Alkynes

They are hydrocarbons having one or more triple bonds between carbon atoms. The general formula for compounds with a triple single bond, is C_nH_2n-2.

Alkynes with a triple single bond.

They are named according to the following standards:

• The longest hydrocarbon chain containing the triple bond is chosen and the termination yne is placed.
• The chain is numbered by the end closest to the triple bond.
• The position of this is indicated by the corresponding locator, which is the lower of the two numbers assigned to the two carbon atoms attached by the triple bond. The locator is placed before the name.

Example:

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Pent-2-yne

• If there are radicals, the main chain will be the longest which contains the triple bond. The numbering will be done corresponding to the two carbon atoms triple bonded the lowest locator possible. The radicals are named like alkanes.

Example:

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3-methylbut-1-yne

Alkynes with several triple bonds.

• If in a compound, there are two or more triple bonds, we use diyne, triyne, etc, endings terminations to name them, rather than yne termination. The chain is numbered assigning to the triple bond carbons with the lowest locators that can be possible.

Example:

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Hexa-1,3,5-triyne.

• If the compound contains radicals, these are named as alkanes, choosing as the hydrocarbon backbone containing the largest number of triple bonds, although it is not the longest one.

Example:

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6-methylhepta-2,4-diyne

Univalent radicals derived from linear alkynes.

They are obtained from alkynes by loss of a hydrogen atom from a terminal carbon. To number it, we will assign this terminal carbon the number 1. They are named by prefixing the corresponding number prefix to completion ynyl.

Examples:

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If the radicals have double bonds, they are first named the double and then triple bonds, indicating its position locators. It is abolishing the “e” of the termination ene.

Examples:

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Unsaturated hydrocarbons with double and triple bonds.

They are hydrocarbons which contain one or more double bonds and one or more triple bonds. The double bonds are first named and then triples ones, pointing its position by locators. It is abolishing the “o” of the termination ene.

• The numbering of the chain will be done by assigning the lowest locators to the unsaturations (double or triple bonds) getting by without if they are double or triple bonds.

Example:

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Hept-3-en-1,6-diyne

• The problem arises when, starting number from the right or left, locators unsaturations are the same. In this case, preference is given to the numbering double bonds, which are assigned with the lower locators.

Example:

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But-1-en-3-yne

You can download the App BioProfe READER to practice this theory with self-corrected exercises.