Advices For Studying Organic Chemistry

ALKENES AND ALKYNES I.

PROPERTIES AND SYNTHESIS

7.1 INTRODUCTION

1. Alkenes are hydrocarbons whose molecules contain the C–C double bond.
   
   
   1. olefin:
      i) Ethylene was called olefiant gas (Latin: oleum, oil + facere, to make) because
      gaseous ethane (C 2 H 4 ) reacts with chlorine to form C 2 H 4 Cl 2 , a liquid (oil).
   
   
   
   

HCCH

Ethene Propene Ethyne

CC

H

H

H

H

CC

H

CH 3

H

H

2. Alkynes are hydrocarbons whose molecules contain the C–C triple bond.
   
   
   1. acetylenes:
   
   
   
   

7.1A PHYSICAL PROPERTIES OF ALKENES AND ALKYNES

1. Alkenes and alkynes have physical properties similar to those of corresponding
   alkanes.

1. Alkenes and alkynes up to four carbons (except 2-butyne) are gases at room
   temperature.


2. Alkenes and alkynes dissolve in nonpolar solvents or in solvents of low polarity.
   i) Alkenes and alkynes are only very slightly soluble in water (with alkynes being
   slightly more soluble than alkenes).
   ii) Alkenes and alkynes have densities lower than that of water.

7.2 NOMENCLATURE OF ALKENES AND CYCLOALKENES

1. Determine the base name by selecting the longest chain that contains the double