Alkenes and Alkynes - How do we Name Alkenes and Alkynes?

12 important questions on Alkenes and Alkynes - How do we Name Alkenes and Alkynes?

How are alkynes named?

By changing the infix -ane- into -yne-.
The parent chain is numbered in the direction that gives the triple bond the lowest number.

What are methylene, vinyl  and allyl?

These are common names. Methylene is a CH2 group.

What systems are there to designate the configuration alkenes?

- The Cis-Trans system.
- The E,Z system
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What is the Cis-Trans system?

Cis means that the orientation of the parent chain atoms is on the same side of the double bond. Trans means they are on opposite sides of the double bond.

What is the E,Z system?

E and Z stand for Entgegen and Zusammen and indicates on what sides the groups of higher priority are.

What are the priority rules for the E,Z system?

The priority is based on atomic number.

How is the priority organized when the first to atoms are the same?

Than it depends on the second atom.

How are carbons that are not sp3 hybridized prioritized?

We treat them as bonded to an equivalent number of atoms to the double or triple bond.

How are cycloalkenes named?

The same as alkenes except for the addition of cyclo- as prefix.

Is it possible to have a trans configuration in cycloalkenes?

Not in the smaller cycloalkenes, but in a cyclooctene it is possible,

What are dienes, trienes and polyenes?

Alkenes having two double bonds are named dienes. With three trienes etc.

What is an example of a biologically important polyene?

Vitamin A, with all the double bonds being cis.

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