Alkynes
Chapter Name : Hydrocarbons |
Sub Topic Code : 102_11_13_04_08 |
Topic Name : Alkynes |
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Sub Topic Name : Addition Reactions |
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Introduction
Alkynes are generally nonpolar molecules with little solubility in polar solvents, such as water. Solubility in nonpolar solvents, such as ether and acetone, is extensive. Like the alkanes and alkenes, alkynes of four or fewer carbon atoms tend to be gases.
Pre-Requisites:
Alkynes
Activity:
Plastics.
Real Life Question:
What is addition reaction?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| addition reaction | An addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Alkynes | Alkynes are generally nonpolar molecules with little solubility in polar solvents, such as water. |
Real life uses :
According to Ferdinand Bohlmann, the first naturally occurring acetylenic compound, dehydromatricaria ester, was isolated from an Artemisia species in 1826. In the nearly two centuries that have followed, well over a thousand naturally occurring acetylenes have been discovered and reported. Polyynes, a subset of this class of natural products, have been isolated from a wide variety of plant species, cultures of higher fungi, bacteria, marine sponges, and corals.
Places to visit :
Chemistry laboratory.
Practical examples around us
| Examples | Explainations |
|---|---|
| ethyne | The chemical compound with the formula C2H2. It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in pure form and thus is usually handled as a solution. Pure acetylene is odorless, but commercial grades usually have a marked odor due to impurities. |
What you learn in Theory:
A carbon-carbon triple bond may be located at any unbranched site within a carbon chain or at the end of a chain, in which case it is called terminal. Because of its linear configuration ( the bond angle of a sp-hybridized carbon is 180º ), a ten-membered carbon ring is the smallest that can accommodate this function without excessive strain. Since the most common chemical transformation of a carbon-carbon double bond is an addition reaction, we might expect the same to be true for carbon-carbon triple bonds. Indeed, most of the alkene addition reactions discussed earlier also takes place with alkynes, and with similar regio- and stereo selectivity.
What you learn in Practice:
The catalytic addition of hydrogen to 2-butyne not only serves as an example of such an addition reaction, but also provides heat of reaction data that reflect the relative thermodynamic stabilities of these hydrocarbons.