Question

How are alkenes obtained?

Answer 1

Alkenes are obtained by elimination reactions

Explanation:

Alkenes are obtained by elimination reactions Following are some examples.

• Dehydration of Alcohol
  In this process alcohol is dehydrated
  (1) byheating with conc.`H_2SO4 at 450K` or by `P_2O_5`
  or (2) by passing alcohol vapor over heated Alumina,`Al_2O_3`

Reaction
`RCH_2CH_2OH->RCH=CH_2+ H_2O`

• Dehydrohalogenation
  In this process Alkyl halide except fluoride is reacted with alcoholic `KOH`
  Reaction
  `RCH_2CH_2X->RCH=CH_2+ HX` (where X =Cl,Br,I)

- Dehalogenation
In this process vicinal or geminal dihalide except fluoride is heated with alcoholic `Zn`

Reaction
`RCHXCH_2X+Zn->RCH=CH_2+ ZnX_2` (where X =Cl,Br,I)

Other process like cracking of alkane is also there