Question

What are the examples of terminal alkynes?

Answer 1

Alkynes refers to that class of group of organic compounds in which a triple bond is present between carbon atoms. The word terminal means the end point. The alkynes which are present at the terminal of the carbon chain known as terminal alkynes.

Complete answer:
Alkynes refers to that class of organic chemistry in which the two carbon atoms are bonded by a triple bond between them. The general formula of alkynes is ${C_n}{H_{2n - 2}}$ , where n is the positive integer whose value is always greater than one. Hence for alkyne we can say that $n \succ 1$. When this alkyne or triple bond is present at the terminal end of the carbon chain then it is known as terminal alkyne.
For example:
$(i){\text{ C}}{{\text{H}}_3} - C \equiv CH$ (Prop-1-yne)
$(ii){\text{ C}}{{\text{H}}_3} - C{H_2} - C \equiv CH$ (But-1-yne)
$(iii){\text{ }}{{\text{C}}_6}{{\text{H}}_5} - C \equiv CH$
Hence we can write the condensed formula for terminal alkynes as: $R - {C_2}H$ where R is any alkyl group.
Properties of terminal alkynes:
A. Terminal alkynes are more acidic in nature as compared to internal alkynes.
B. Terminal alkynes are more stable than internal alkynes.
C. The terminal alkynes are more reactive towards electrophilic addition reaction.
D. There is no steric hindrance in case of terminal alkynes.

Note:
Terminal alkynes are present on the terminal end of the parent carbon chain. The value of n in the general formula of alkynes cannot be equal to one or less than one as it will violate the structure of alkynes. The hybridization of alkyne carbon atoms is always sp. The triple bond consists of two sigma bonds and one pi bond. The presence of alkyne in the carbon chain increases the acidity of the carbon chain.