Question

COCl2 how many lone pairs around the central atom? COCl2 Compared to the ideal angle you would expect the actual angle between the silicon oxygen bonds to be about the same, bigger, or smaller

Answer 1

In COCl2 the central atom is carbon atom. Total number of valance electrons in COCl2= 4 electron from valance shell(c) + 2 electron from two chlorine atom+ 2 electron from oxygen atom= 8 eletrons=4 bond pair.

Now, Carbon Oxygen bond contain two bond pairs ( 1 sigma + 1 pi bond)and Two C-Cl bond contain two bond pais. i.e no lone pairs present around the central atom.

In case of SOCl2, the central atom is replaced by sulphur atom. Total number of valance electrons in SOCl2= 6 electron from the valance shell(S) + 2 electron from oxygen atom+ 2 electron from the two chlorine atom= 10 electron= 5 bond pairs.

Now, Sulphur Oxygen contain two bond pairs(1 sigma + 1 pi bond), two Sulphur Chlorine bond contain two bond pairs and one lone pair present in the central atom.

Now according to VSEPR theory : Lone pair- lone pair repulsion> Lone pair- bond pair> bond pair - bond pair repulsion. So in a molecule due to this various repulsion the bonds are arranged in such a arrangement having lower repulsion.In comparison between COCl2 and SOCl2 , SOCl2 contain one lone pair and it repeals(lp-bp repulsion) other bond pairs so the bond angles is decrease. But in case of COCl2 such phenomenon is not occur.Hence it is concluded that the bond angle of silicon oxygen bonds are smaller than the carbon oxygen bonds.

Approximate bond angles, COCl2 bond angle = 120 degree and SOCl2 bond angle= 109.5 degree