Alkynes
Chapter Name : Hydrocarbons |
Sub Topic Code : 102_11_13_04_04 |
Topic Name : Alkynes |
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Sub Topic Name : Preparation From Vicinal Dihalides |
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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:
Vicinal Dihalides
Activity:
Graphite.
Real Life Question:
What are alkynes?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| Vicinal Dihalides | It is a compound in which two halogen atoms are attached to two adjacent carbon atoms. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| organ halogen compound | Treatment of a geminal dihalide (both halogens on the same carbon) or a vicinal dihalide (halogens on adjacent carbons) with a base such as sodium ethoxide (NaOCH2CH3) yields a vinylic halide. |
Real life uses :
In the artificial ripening of fruit, calcium carbide is sometimes used as source of acetylene gas, which is a ripening agent similar to ethylene.
Places to visit :
Chemistry laboratory.
Practical examples around us
| Examples | Explainations |
|---|---|
| Carbide lamps | Calcium carbide is used in carbide lamps, in which water drips on the carbide and the acetylene formed is ignited. These lamps were usable but dangerous in coal mines, where the presence of the flammable gas methane made them a serious hazard. The presence of flammable gases in coal mines led to miner safety lamps such as the Davy lamp, in which a wire gauze reduces the risk of methane ignition. |
What you learn in Theory:
Vicinal dihalides, compounds that have halogens on adjacent carbons, are prepared by the reaction between a halogen and an alkene. The simplest example is the reaction between ethylene and chlorine to give 1, 2-dichloroethane (ethylene dichloride).
What you learn in Practice:
Vicinal dihalides is prepared by the method of halogenation from alkene.