JEE Main & Advanced Chemistry Hydrocarbons / हाइड्रोकार्बन Alkenes

These are the acyclic hydrocarbon in which carbon-carbon contain double bond. These are also known as olefins, because lower alkene react with halogens to form oily substances. General formula is  \[{{C}_{n}}{{H}_{2n}}\]. Examples, \[{{C}_{2}}{{H}_{4}},\,{{C}_{3}}{{H}_{6}},\,{{C}_{4}}{{H}_{8}}\].

(1) Preparation methods

(i) From Alkynes :

\[R-C\equiv C-R+{{H}_{2}}\underset{Pd.\,BaS{{O}_{4}}}{\mathop{\xrightarrow{\text{Lindlar }\!\!'\!\!\text{ s}\,\text{Catalyst}}}}\,R-\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,=\underset{H}{\mathop{\underset{|}{\mathop{C}}\,}}\,-R\]

• Poison’s catalyst such as \[BaS{{O}_{4}},\,CaC{{O}_{3}}\] are used to stop the reaction after the formation of alkene.

(ii) From mono halides :

\[R-\overset{H}{\mathop{\overset{|}{\mathop{\underset{H}{\mathop{\underset{|}{\mathop{C}}\,}}\,}}\,}}\,-\overset{H}{\mathop{\overset{|}{\mathop{\underset{X}{\mathop{\underset{|}{\mathop{C}}\,}}\,}}\,}}\,-H+Alc.\,KOH\xrightarrow[-HX]{}\underset{\text{Alkene}}{\mathop{R-\underset{H}{\mathop{\underset{|}{\mathop{C}}\,}}\,=}}\,\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,-H\]

• If we use alc. \[NaOH\] in place of \[KOH\] then trans product is formed in majority because of its stability. According to saytzeff rule.

(iii) From dihalides

(a) From Gem dihalides

 

• If we take two different types of gemdihalides then we get three different types of alkenes .
• Above reaction is used in the formation of symmetrical alkenes only.

(b) From vicinal dihalides :

\[R-\overset{H}{\mathop{\overset{|}{\mathop{\underset{X}{\mathop{\underset{|}{\mathop{C}}\,}}\,}}\,}}\,-\overset{H}{\mathop{\overset{|}{\mathop{\underset{X}{\mathop{\underset{|}{\mathop{C}}\,}}\,}}\,}}\,-H+Zn\,dust\underset{{{300}^{o}}C}{\mathop{\xrightarrow{\Delta }}}\,R-\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,=\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,-H+Zn{{X}_{2}}\]

• Alkene is not formed from 1, 3 dihalides. Cycloalkanes are formed by dehalogenation of it.

 

(iv) By action of  on vicinal dihalide : 

 

 

(v) From alcohols [Laboratory method] :

 

\[\underset{\text{Ethyl alcohol}}{\mathop{C{{H}_{3}}C{{H}_{2}}OH}}\,\underset{443\,K}{\mathop{\xrightarrow{{{H}_{2}}S{{O}_{4}}\,or\,{{H}_{3}}P{{O}_{4}}}}}\,\underset{\text{Ethene}}{\mathop{C{{H}_{2}}}}\,=C{{H}_{2}}+{{H}_{2}}O\]

 

(vi) Kolbe’s reaction :

 

\[\underset{\text{Potassium succinate}}{\mathop{\begin{array}{*{35}{l}} C{{H}_{2}}COOK  \\ \,|  \\ C{{H}_{2}}COOK  \\ \end{array}}}\,+2{{H}_{2}}O\xrightarrow{\text{Electrolysis}}\underset{\text{Ethene}}{\mathop{\begin{array}{*{35}{l}} C{{H}_{2}}  \\ \,|  \\ C{{H}_{2}}  \\ \end{array}}}\,+2C{{O}_{2}}+{{H}_{2}}+2KOH\]

 

(vii) From esters [Pyrolysis of ester] :

 

\[C{{H}_{3}}-CO-\underset{C{{H}_{2}}-C{{H}_{2}}}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,}{\mathop{O\,\,\,\,\,\,\,\,\,\,\,\,H\,\,\,\,\,\,}}\,}}\,\underset{liq.\,{{N}_{2}}}{\mathop{\begin{align} &  \\  & \xrightarrow{\text{Glass}\,\text{wool}\,{{450}^{o}}} \\  \end{align}}}\,\underset{C{{H}_{2}}=C{{H}_{2}}}{\mathop{\underset{+}{\mathop{C{{H}_{3}}-COOH}}\,}}\,\]

 

(viii) Pyrolysis of quaternary ammonium compounds :

\[\underset{\underset{\text{hydroxide}}{\mathop{\text{Tetraethyl}\,\text{ammonium}}}\,}{\mathop{{{({{C}_{2}}{{H}_{5}})}_{4}}\overset{+}{\mathop{N}}\,\overset{-}{\mathop{OH}}\,}}\,\xrightarrow{heat}\underset{\underset{\text{(Tert}\text{.}\,\text{amine)}}{\mathop{\text{Triethylamine}}}\,}{\mathop{{{({{C}_{2}}{{H}_{5}})}_{3}}N}}\,+\underset{\text{Ethene}}{\mathop{{{C}_{2}}{{H}_{4}}}}\,+{{H}_{2}}O\]

(ix) Action of copper alkyl on vinyl chloride :

\[\underset{\text{Vinyl}\,\text{chloride}}{\mathop{{{H}_{2}}C=CHCl}}\,\xrightarrow{Cu{{R}_{2}}}{{H}_{2}}C=CHR\]

(x) By Grignard reagents :

 

 

(xi) The wittig reaction :

\[{{(Ph)}_{3}}P=C{{H}_{2}}+\underset{O\,\,\,}{\mathop{\underset{|\,|\,\,\,\,}{\mathop{CH}}\,}}\,-R\xrightarrow{{}}{{(Ph)}_{3}}P=O+R-\underset{C{{H}_{2}}}{\mathop{\underset{|\,|\,\,\,\,\,\,}{\mathop{CH\,}}\,}}\,\]

 

\[{{(Ph)}_{3}}P=CH-R+\overset{O\,\,\,}{\mathop{\overset{|\,|\,\,\,\,}{\mathop{CH}}\,}}\,-R\xrightarrow{{}}{{(Ph)}_{3}}P=O+R-CH=CH-R\]

 

(xii) From \[\beta \]bromo ether [Boord synthesis]

 

 

(2) Physical Properties

(i) Alkenes are colourless and odourless.

(ii) These are insoluble in water and soluble in organic solvents.

(iii) Physical state

\[{{C}_{1}}-{{C}_{4}}\xrightarrow{{}}\] gas

\[{{C}_{4}}-{{C}_{16}}\xrightarrow{{}}\] liquid

\[>\,\,\,{{C}_{17}}\xrightarrow{{}}\] solid wax

(iv) B.P. and M.P. decreases with increasing branches in alkene.

(v) The melting points of cis isomers are lower than trans isomers because cis isomer is less symmetrical than trans. Thus trans packs more tightly in the crystal lattice and hence has a higher melting point.

 

(vi) The boiling points of cis isomers are higher than trans isomers because cis-alkenes has greater polarity (Dipole moment) than trans one.

 

(vii) These are lighter than water.

(viii) Dipole moment : Alkenes are weakly polar. The, \[\pi -\]electron’s of the double bond. Can be easily polarized. Therefore, their dipole moments are higher than those of alkanes.

 

(3) Chemical properties

 

(i) Francis experiment : According to Francis electrophile first attacks on olefinic bond.

 

(ii) Reaction with hydrogen :

 

\[R-\overset{H\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,|}{\mathop{C=C}}\,}}\,-R+{{H}_{2}}\xrightarrow{Ni}R-\underset{H\,\,\,H}{\mathop{\underset{|\,\,\,\,\,\,\,|}{\mathop{\overset{H\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,|}{\mathop{C-C}}\,}}\,}}\,}}\,-R\]

 

(iii) Reduction of alkene via hydroboration : Alkene can be converted into alkane by protolysis

\[RCH=C{{H}_{2}}\xrightarrow{H-B{{H}_{2}}}{{(R-C{{H}_{2}}-C{{H}_{2}})}_{3}}B\]

\[\xrightarrow{{{H}^{+}}/{{H}_{2}}O}R-C{{H}_{2}}-C{{H}_{3}}\]

 

 

Hydroboration : Alkene give addition reaction with diborane which called hydroboration. In this reaction formed trialkylborane, Which is very important and used for synthesis of different organic compound

 

 

The overall result of the above reaction appears to be antimarkownikoff’s addition of water to a double bond.

 

(iv) By treatment with \[\mathbf{AgN}{{\mathbf{O}}_{\mathbf{3}}}\mathbf{+NaOH}\] :  This reaction gives coupling

\[6C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\overset{C{{H}_{3}}}{\mathop{\overset{|\,\,\,\,\,\,\,\,}{\mathop{C\,\,=\,\,\,}}\,}}\,C{{H}_{2}}\xrightarrow{{{B}_{2}}{{H}_{6}}}\]

\[2{{[C{{H}_{3}}-{{(C{{H}_{2}})}_{2}}-\underset{H\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,}{\mathop{\overset{C{{H}_{3}}}{\mathop{\overset{|\,\,\,\,\,\,\,\,}{\mathop{C\,\,-\,\,}}\,}}\,}}\,}}\,C{{H}_{2}}]}_{3}}B\xrightarrow{Ag/N{{O}_{3}}NaOH}\]

\[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-\underset{H\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,}{\mathop{\overset{C{{H}_{3}}}{\mathop{\overset{|\,\,\,\,\,\,\,\,}{\mathop{C\,\,-\,\,}}\,}}\,}}\,}}\,C{{H}_{2}}-C{{H}_{2}}-\underset{H\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,}{\mathop{\overset{C{{H}_{3}}}{\mathop{\overset{|\,\,\,\,\,\,\,\,}{\mathop{C\,\,-\,\,}}\,}}\,}}\,}}\,C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}\]

 

(v) Birch reduction : This reaction is believed to proceed via anionic free radical mechanism.

\[R-CH=C{{H}_{2}}\underset{+{{e}^{-}}}{\mathop{\xrightarrow{Na}}}\,R-C\overset{-}{\mathop{H}}\,-C{{\overset{-}{\mathop{H}}\,}_{2}}\xrightarrow{Et-O-H}\]\[R-CH-C{{H}_{3}}\]

\[\underset{+{{e}^{-}}}{\mathop{\xrightarrow{Na}}}\,R-\overset{-}{\mathop{\underset{{}}{\mathop{C}}\,}}\,H-C{{H}_{3}}\xrightarrow{Et.-O-H}R-C{{H}_{2}}-C{{H}_{3}}\]

 

(vi) Halogenation 

\[\underset{\text{Propene}}{\mathop{C{{H}_{3}}CH=C{{H}_{2}}}}\,+C{{l}_{2}}\xrightarrow{{{500}^{o}}C}\underset{\text{or 3-Chloro-1-propene}}{\mathop{\underset{\text{Allyl}\,\text{chloride}}{\mathop{ClC{{H}_{2}}-CH=C{{H}_{2}}}}\,}}\,+HCl\]

• If NBS [N-bromo succinimide] is a reagent used for the specific purpose of brominating alkenes at the allylic position.

                                       

 

• In presence of polar medium alkene form vicinal dihalide with halogen. 

 

\[R-\overset{H\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,|}{\mathop{C=C}}\,}}\,-H+X-X\xrightarrow{CC{{l}_{4}}}\underset{\text{Vicinal dihalide}}{\mathop{R-\underset{X\,\,\,X}{\mathop{\underset{|\,\,\,\,\,\,\,|}{\mathop{\overset{H\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,|}{\mathop{C-C}}\,}}\,}}\,}}\,-H}}\,\]

Reactivity of halogen is  \[{{F}_{2}}\,\,>\,\,\,C{{l}_{2}}\,\,>\,\,\,B{{r}_{2}}\,\,\,>\,\,\,{{I}_{2}}\]

 

(vii) Reaction with HX [Hydrohalogenation]

 

 

According to markownikoff’s rule and kharasch effect.

\[C{{H}_{3}}-CH=C{{H}_{2}}+HBr\xrightarrow{{}}C{{H}_{3}}-\overset{H\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,|}{\mathop{\underset{Br\,\,\,H}{\mathop{\underset{|\,\,\,\,\,\,\,\,|}{\mathop{C-C}}\,}}\,}}\,}}\,-H\]

According to Anti Markownikoff rule     (Based on F.R.M.)

\[C{{H}_{3}}-CH=C{{H}_{2}}+HBr\xrightarrow{\text{Peroxide}}\]

\[\underset{(\text{minor)}}{\mathop{C{{H}_{3}}-\overset{H\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,|}{\mathop{\underset{Br\,\,\,H}{\mathop{\underset{|\,\,\,\,\,\,\,\,|}{\mathop{C-C}}\,}}\,}}\,}}\,-H}}\,\,+\,\underset{\text{(major)}}{\mathop{C{{H}_{3}}-\overset{H\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,|}{\mathop{\underset{H\,\,\,Br}{\mathop{\underset{|\,\,\,\,\,\,\,\,|}{\mathop{C-C}}\,}}\,}}\,}}\,-H}}\,\]

 

(viii) Reaction with hypohalous acids :

\[\underset{\text{Ethylene}}{\mathop{C{{H}_{2}}=C{{H}_{2}}}}\,+H\overset{-}{\mathop{O}}\,\overset{+}{\mathop{Cl}}\,\xrightarrow{{}}\underset{\text{Ethylene chlorohydrin}}{\mathop{C{{H}_{2}}OH.C{{H}_{2}}Cl}}\,\]

• In case of unsymmetrical alkenes markownikoff rule is followed.

(ix) Reaction with sulphuric acid :

\[\underset{\text{Ethylene}}{\mathop{C{{H}_{2}}=C{{H}_{2}}}}\,+{{H}^{+}}HSO_{4}^{-}\xrightarrow{{}}\underset{\text{Ethyl hydrogen sulphate}}{\mathop{C{{H}_{3}}C{{H}_{2}}HS{{O}_{4}}}}\,\]

\[C{{H}_{3}}C{{H}_{2}}HS{{O}_{4}}\xrightarrow{{}}C{{H}_{2}}=C{{H}_{2}}+{{H}_{2}}S{{O}_{4}}\]

 

• This reaction is used in the seperation of alkene from a gaseous mixture of alkanes and alkenes.

(x) Reaction with nitrosyl chloride

 (\[NOCl\] is called Tillden reagent)

• If hydrogen is attached to the carbon atom of product, the product changes to more stable oxime.

 

 

(xi) Oxidation : With alkaline \[KMn{{O}_{4}}\] [Bayer’s reagent] :  This reaction is used as a test of unsaturation.

\[R-\overset{\,H\,\,\,\,H}{\mathop{\overset{\,|\,\,\,\,\,\,\,\,|}{\mathop{C=C}}\,}}\,-H+[O]+H-OH\underset{-OH}{\mathop{\xrightarrow{Alk\,KMn{{O}_{4}}}}}\,\underset{\text{glycol}}{\mathop{R\overset{H\,\,\,\,\,\,H}{\mathop{\overset{|\,\,\,\,\,\,\,\,\,|}{\mathop{\underset{HO\,\,\,\,OH}{\mathop{\underset{\,\,|\,\,\,\,\,\,\,\,|}{\mathop{-C-C}}\,-}}\,}}\,}}\,H}}\,\]

With acidic \[KMn{{O}_{4}}\] :

\[R-\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,=\overset{H}{\mathop{\overset{|}{\mathop{C}}\,}}\,-H+[O]\underset{KMn{{O}_{4}}}{\mathop{\xrightarrow{acidic}}}\,R-\overset{O}{\mathop{\overset{|\,|}{\mathop{C}}\,}}\,-O-H+C{{O}_{2}}+{{H}_{2}}O\]

(xii) Hydroxylation

(a) Using per oxy acid  :

\[\underset{\text{2-Butene}}{\mathop{\overset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\overset{\,\,\,\,\,\,\,\,\,|}{\mathop{\underset{\,\,\,\,\,\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{\,\,\,\,\,\,\,\,\,|}{\mathop{\underset{H-C}{\mathop{\underset{\,\,\,\,\,\,\,\,\,||}{\mathop{H-C}}\,}}\,}}\,}}\,}}\,}}\,}}\,\underset{or\,HC{{O}_{3}}H}{\mathop{\xrightarrow{{{H}_{2}}{{O}_{2}},\,HCOOH}}}\,\underset{\text{Trans (racemic)}}{\mathop{\overset{\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\overset{\,\,\,\,|}{\mathop{\underset{\,\,\,\,\,\,\,\,\,C{{H}_{3}}}{\mathop{\underset{\,\,\,\,|}{\mathop{\underset{HO-C-H}{\mathop{\underset{\,\,\,\,|}{\mathop{\,\,\,\,\,\,\,\,H-C-OH}}\,}}\,}}\,}}\,}}\,}}\,}}\,\]

 

(b) Hydroxylation by \[Os{{O}_{4}}\]:

• If per benzoic acid or peroxy acetic acid is used then oxirane are formed.

\[R-CH=CH-R\underset{or\,C{{H}_{3}}C{{O}_{3}}H}{\mathop{\xrightarrow{{{C}_{6}}{{H}_{5}}C{{O}_{3}}H}}}\,R-\underset{OH}{\mathop{\underset{|\,\,\,\,\,}{\mathop{CH}}\,}}\,-\underset{OH}{\mathop{\underset{|\,\,\,\,\,}{\mathop{CH}}\,}}\,-R\xrightarrow{-{{H}_{2}}O}\]   \[\underset{\text{ }\!\![\!\!\text{ Oxirane }\!\!]\!\!\text{ }}{\mathop{R-\underset{O\,\,\,}{\mathop{\underset{{}}{\mathop{CH-CH}}\,}}\,-R}}\,\]

(xiii) Combustion : \[{{C}_{n}}{{H}_{2n}}+\frac{3n}{2}{{O}_{2}}\xrightarrow{{}}nC{{O}_{2}}+n{{H}_{2}}O\]

They burn with luminous flame and form explosive mixture with air or oxygen.

 (xiv) Ozonolysis

  

 

• Application of ozonolysis : This process is quite useful to locate the position of double bond in an alkene molecule. The double bond is obtained by Joining the carbon atoms. of the two carbonyl compounds.

 

(xv) Oxy – mercuration demercuration : With mercuric acetate (in THF), followed by reduction with \[NaB{{H}_{4}}/NaOH\] is also an example of hydration of alkene according to markownikoff’s rule.

\[\underset{\text{3,3-dimethyl-1-butene}}{\mathop{{{(C{{H}_{3}})}_{3}}C-CH=C{{H}_{2}}}}\,+\underset{\text{Mercuric acetate}}{\mathop{{{(C{{H}_{3}}COO)}_{2}}Hg}}\,\xrightarrow{{}}\]

\[{{(C{{H}_{3}})}_{3}}C-\underset{OCOC{{H}_{3}}}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{CH-C{{H}_{2}}}}\,}}\,-Hg\underset{THF}{\mathop{\xrightarrow{NaB{{H}_{4}}/NaOH}}}\,\underset{3,\,3-\text{Dimethyl}-\text{2}-\text{butanol}}{\mathop{{{(C{{H}_{3}})}_{3}}C-\underset{OH}{\mathop{\underset{|\,\,\,\,\,}{\mathop{CH}}\,}}\,-C{{H}_{3}}}}\,\]

 

(xvi) Epoxidation

(a) By \[{{O}_{2}}/Ag\]  : 

(b) Epoxidation by performic acid or perbenzoic acid :

(xvii) Hydroboration

\[3R-CH=C{{H}_{2}}+B{{H}_{3}}\xrightarrow{{}}\underset{\text{Tri alkyl borane}}{\mathop{{{(R-C{{H}_{2}}-C{{H}_{2}})}_{3}}B}}\,\xrightarrow{{{H}_{2}}{{O}_{2}}/O{{H}^{-}}}R-C{{H}_{2}}-C{{H}_{2}}-OH+B{{(OH)}_{3}}\]

\[R-C{{H}_{2}}-C{{H}_{2}}-OH+B{{(OH)}_{3}}\]

(Anti markownikoff’s rule)

(xviii) Hydroformylation :

\[R-CH=C{{H}_{2}}+CO+{{H}_{2}}\xrightarrow{CoH{{(CO)}_{4}}}\underset{\,\,\,\,\,\,\,H}{\overset{\,\,\,\,\,\,\,\,\,H}{\mathop{\underset{\,\,\,\,\,\,\,\,|}{\overset{\,\,\,\,\,\,\,\,\,|}{\mathop{R-C}}}\,}}}\,-\underset{H\,\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,}{\mathop{\underset{C\,=\,O\,}{\mathop{\overset{H\,\,\,\,\,\,}{\mathop{\underset{|\,\,\,\,\,\,\,\,}{\mathop{\overset{|\,\,\,\,\,\,\,\,}{\mathop{C-H}}\,}}\,}}\,}}\,}}\,}}\,\]

 

• If \[CO+{{H}_{2}}O\] is taken then respective acid is formed.

\[R-CH=C{{H}_{2}}+CO+{{H}_{2}}O\xrightarrow{CoH{{(CO)}_{4}}}R-C{{H}_{2}}-\underset{COOH}{\mathop{\underset{|\,\,\,\,\,\,\,\,\,\,\,\,}{\mathop{C{{H}_{2}}\,\,\,\,}}\,}}\,\]

(xix) Addition of formaldehyde  

\[{{H}_{2}}C=O+\overset{\oplus }{\mathop{H}}\,\xrightarrow{{}}[{{H}_{2}}C=\overset{\oplus }{\mathop{O}}\,H\overset{{}}{\longleftrightarrow}{{H}_{2}}\overset{\oplus }{\mathop{C}}\,-OH]\]

\[\xrightarrow{R-CH=C{{H}_{2}}}R-\overset{\oplus }{\mathop{C}}\,H-C{{H}_{2}}-C{{H}_{2}}-OH\frac{\,\,\,\,\,HOH\,\,\,\,}{-{{H}^{+}}}\]

 

(xx) Polymerisation

 

 

• If in polymerisation zeigler- natta catalyst \[[{{(R)}_{3}}Al+TiC{{l}_{4}}]\] is used then polymerisation is known as zeigler-natta polymerisation.

(xxi) Isomerisation :

\[C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-CH=C{{H}_{2}}\]

\[\]\[C{{H}_{3}}-C{{H}_{2}}-CH=CH-C{{H}_{3}}\]

The mechanism proceeds via carbocation.

(xxii) Addition of \[HN{{O}_{3}}\] :

\[\underset{\text{Ethene}}{\mathop{C{{H}_{2}}=C{{H}_{2}}}}\,+HO-N{{O}_{2}}\xrightarrow{{}}\underset{\text{2-Nitroethanol}}{\mathop{C{{H}_{2}}OH.C{{H}_{2}}N{{O}_{2}}}}\,\]

(xxiii) Addition of Acetyl chloride :

\[\underset{\text{Ethene}}{\mathop{C{{H}_{2}}=C{{H}_{2}}}}\,+C{{H}_{3}}COCl\xrightarrow{{}}\underset{\text{4-Chlorobutanone-2}}{\mathop{C{{H}_{2}}ClC{{H}_{2}}COC{{H}_{3}}}}\,\]

(4) Uses

(i) For the manufacture of polythene – a plastic material;   (ii) For artificial ripening of fruits; (iii) As a general anaesthetic; (iv) As a starting material for a large number of compounds such as glycol, ethyl halides, ethyl alcohol, ethylene oxide, etc; (v) For making poisonous mustard gas (War gas);  (vi) For making ethylene-oxygen flame.