Alkynes
Chapter Name : Hydrocarbons |
Sub Topic Code : 102_11_13_04_06 |
Topic Name : Alkynes |
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Sub Topic Name : Chemical Properties |
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Introduction
In organic chemistry, an alkyne is an unsaturated hydrocarbon which has at least one carbon-carbon triple bond between two carbon atoms. The simplest acyclic alkynes with only one triple bond and no other functional groups form a homologous series with the general chemical formula CnH2n-2.
Pre-Requisites:
Alkynes
Activity:
Plastics.
Real Life Question:
What are alkynes?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| IUPAC nomenclature | The IUPAC nomenclature of organic chemistry is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). Ideally, every possible organic compound should have a name from which an unambiguous structural formula can be created. |
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 :
Alkanes are our fuels. From the gases, methane, to butane, The liquid fuel for cars, in theory about C8 alkanes, Kerosene for heating and aircraft, All the way up to heavy fuel oils.
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:
Alkynes are characteristically more unsaturated than alkenes. Thus they add two equivalents of bromine whereas an alkene adds only one equivalent. Other reactions are listed below. Alkynes are usually more reactive than alkenes. They show greater tendency to polymerize or oligomerize than alkenes do. The resulting polymers, called polyacetylenes (which do not contain alkyne units) are conjugated and can exhibit semiconducting properties.
What you learn in Practice:
In acetylene, the H–C?C bond angles are 180°. By virtue of this bond angle, alkynes tend to be rod-like. Correspondingly, cyclic alkynes are rare. Benzyne is highly unstable. The C?C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C-C bond in alkanes (153 pm).