What is the index of hydrogen deficiency of the compound C10H13NO?

Question

Please show how to answer this (if possible)

Answer 1

The Index of Hydrogen Deficiency (IHD), is a count of how many molecules of H2 need to be added to a structure in order to obtain the corresponding saturated, acyclic species.

Hence it takes a count of how many rings and multiple bonds are present in the structure, so IHD can also be thought of as (multiple bonds + rings) or (p + r).

When you look at a structure, just count them up (but take care not to count any rings twice !)

If you have a molecular formula, CcHhNnOoXx, then the following equation can be derived:

IHD = 0.5 * [2c+2-h-x+n]

The maximum number of hydrogen atoms for "c" carbon atoms is 2c+2 (think of the formulae of saturated hydrocarbons such as ethane, propane etc.).

From this number, subtract the "h" hydrogens that you have.

Since, like hydrogen, a halogen only forms one bond, then they can be treated as if they are hydrogens, so subtract them as well.

Oxygen forms two bonds, therefore it has no impact (compare H count for methane, CH4, and methanol, CH3OH).

Nitrogen forms three bonds. This means for "n" nitrogens, "n" extra hydrogen atoms are needed (compare the H count for methane, CH4, and methyl amine, CH3NH2), therefore, add "n".

The factor of 0.5 accounts for us counting H atoms, but adding hydrogen, H2 , molecules. OK ? You should now be able to do this yourself.