Question

Do you know the carbon chain lengths for the different states of alkynes?

Eg alkanes having a carbon chain length of 1-4 are gases, 5-16 are liquids and 17+ are solids.

Are there similar rules for alkynes?

Answer 1

Not really. Ethyne and propyne have m.p. at -82^o and -101 C respectively with boiling poing of -75 and -23 respectively. Therefore, both are gases. The m.p. of all the others are below -24 and the boiling points rise from 9 with 1-butyne, 40 for 1-pentyne, 72 for 1-hexyne, 100 for 1-heptyne, 126 for 1 octyne, etc, increasing as molar mass increases. The isomers (2-butyne at 27 C, 2-pentyne at 55, 2-hexyne at 84) start another increasing series.