3 . From unsaturated hydrocarbons : -Sabatier-Senderens reduction
R CH CH2 H2 |
Ni / |
R CH2 |
CH3 |
R C CH H2 |
Ni / |
R CH2 |
CH3 |
4 . From carboxylic acids-Decarboxylation- Kolbe ’ s electrolytic method-
Physical Properties : -
( 1 ) Nature : - Non-Polar due to covalent nature of C — C bond and C — H bond . C — C bond enrgy = 83 kj / mole and C — H bond energy = 99 kj / mole . C1 —
C4 = gases , C5 — C17 = colourless odourless liquid and > C17 = Solid .
( 2 ) Solubility : - Like dissolve like Viz , Polar compounds dissolve in polar solvent and Non-Polar compound dissolve in non polar solvent .
( 3 ) Boiling point : - Low boiling point due to non polar in nature .
The molecules are held together only by weak Van der Waalls ’ forces . Since we known that the magnitude of Van der Waalls ’ forces is directly proportional to the molecular size . Therefore , the boiling point increases with increase the molecular size i . e . with increase in number of carbon atoms .
Noted : - the boiling points of the branched chain Alkanes are less than the straight chain isomers .
This is due to the fact that branching of the chain makes the molecule more compact and thereby decreases the surface aria and consequently , the magnitudes of Van der Waalls ’ forces also decrease .
CH CH CH CH CH H C — CH — CH CH CH 3
3 2 2 2 3
3 2 3
n-pentane CH H 3C — C — CH 3
3 boiling point = 309 K iso-pentane CH 3 neo-pentane