Unsaturated hydrocarbons

Unsaturated hydrocarbons contains one or more carbon-carbon double bond, triple bonds or benzene-like rings.

1. UNSATURATED HYDROCARBONS

2. ALKENES - an unsaturated hydrocarbon that contains a carbon-carbon double bond. Unsaturated hydrocarbons contains one or more carbon-carbon double bond, triple bonds or benzene-like rings.

3. ALKYNES - are unsaturated hydrocarbon that contains a carbon-carbon triple bond. The simplest alkene is ETHYLENE ( CH₃=CH₂ ) The simplest alkyne is ACETYLENE ( H-C≡C-H )

4. THERMAL CRACKING- a saturated hydrocarbon converted to an unsaturated hydrocarbon plus H₂. EXAMPLE: CH₂CH₃ CH₂=CH₂ + H₂ thermal cracking (800-900⁰C)

5. GEOMETRIC ISOMERISM OF ALKENE CIS- TRANS ISOMERISM - isomer that have the same connectivity of their atoms but a different arrangement of their atoms in space - cis and trans stereoisomers results from the presence of either a ring or a carbon-carbon double bond.

6. How do we names ALKENE and ALKYNE? The key to IUPAC systems of naming alkenes using sa suffix – ene that tells us that it contain a carbon-carbon double bond. Find the longest carbon chain that includes the double bond. Indicate the length of the parent chain by using a prefix that tells the number of carbon atoms.

7. 3. Branched alkenes are named in a manner similar to alkane, substituent groups are located and named . 2. Number the chain from the end that gives the lower set of numbers to the carbon atoms of the double bond . Designate the position of the double bond by the number of its carbon.

8. The key to IUPAC names of an alkyne is using the suffix – yne which shows the presence of a carbon- carbon triple bond. In the higher alkynes, number the longest carbon chain that contains the triple bond from the end that gives the lower set of numbers to the triply bond carbons. Indicate the location of the triple bond by the number of its first carbon atom.

9. Cycloalkenes In naming cycloalkenes , number the carbon atoms of the ring double bond 1 and 2 in the direction that gives the substituent encountered first the lower number. 3-methylcyclopentene 4-ethyl -1-methylcyclohexe

10. Dienes , trienes and polyenes We name alkenes that contains more than one double bond as alkadienes,alkatrienes and so on. To those that contain several double bonds more generally called polyenes . Examples: CH₂=CHCH₂CH=CH₂ 1,4- Pentadiene CH₂ CH₂=CCH=CH₂ 2-methyl1,3-butadiene 1,3-cyclopentadiene

11. Physical properties of alkenes and alkynes They are non-polar compounds Alkenes and alkynethat are liquid at room temperature have densities less than 1.0 g/ml. They are insoluble in water but not soluble in one another and in other non-polar organic liquids.