Bent rule

A very short presentation. The topic adapted from inorganic chemistry

1. Topic : Bent’s Rule B y : Aman Kumar M.Sc . Integrated Chemistry

2. Bent’s Rule Bent’s rule describes and explains the relationship between the orbital hybridization of central atoms in molecules and the electronegativities of substituents. The rule was started by Henry Bent as follow : more electronegativity element prefer hybrid orbital having less s character and more p character while less electronegative substituents prefer hybrid orbital having more s character. Examples ; CH 4 , CH 3 F

3. Example fluoromethane justification Due to non – uniform distribution of % S character the bond angle change due to decreases % S character in F- bond the bond angle decreases.

4. Application of bent rule Bond length : Bond length depends upon the hybridization of the atom. Let’s take an example of chloromethane having average C-Cl bond length 1.783 Å and some other bond lengths shown in table A. As the electronegativity of chlorine atom is very high than hydrogen therefore, in chloromethane the carbon will direct a hybrid orbital high in p character towards chlorine. On the other hand orbitals have high s character direct towards the hydrogen. Bond length is proportional to % of s character. Table A : bond length

5. Application of bent rule Bond angle : Bent rule can explain the difference in the bond angles of molecules from ideality . The relation between the hybridization of central metal atom and bond angle can be explain by taking example of methane. According to bent rule, as the electronegativity of the substituent increases, orbitals having greater p character will be directed towards those groups and hence the bond angle decreases. It suggests that the hybrid orbital having more s character should be directed towards the hydrogen having more p character. Bond angle is proportional to % s character.