Index of hydrogen deficiency

Index of hydrogen deficiency

1. Prepared by MAHENDRA.G.S M pharm Pharmaceutical chemistry J S S College of Pharmacy Mysuru Index of Hydrogen Deficiency (IHD)

2. The index of hydrogen deficiency is no. of pairs of hydrogen atom t hat must be removed from the corresponding “ saturated” formula to produce the molecular formula of the compound of interest. The index of hydrogen deficiency is also called the number of “ sites(or degree) of unsaturation”; Index of Hydrogen Deficiency (IHD)

3. Description is incomplete since hydrogen deficiency can result from cyclic structures as well as from multiple bonds. The index is thus the sum of the number of rings, the number of double bonds, and twice the number of double bonds, and twice the number of triple bond. The index of hydrogen deficiency can be calculated for compounds containing C,N,H,O,S, and halogen from the formula .

4. Formula for index hydrogen deficiency Index   Thus , the compound C 7 H 7 NO has an index of 7-3.5+0.5+1=5. Note that divalent atoms (O,S) are not counted in the formula . For the generalized molecular formula α i β ii γ iii δ iv The index =IV-1/2I+1/2III+1,where . α is H,D, or halogen (i.e. any monovalent atom) β is O, S, or any other bivalent atom. γ is N,P, or any other trivelant atom δ is C,Si, or any other tetravalent

5. The numerals I-IV designate the numbers of the mono-,di-,tri-,and tetravalent atoms respectively. For simple molecular formulas, we can arrive at the index by comparison of the formula of interest With the molecular formula of the corresponding saturated compound . Compare C6H6 and C6H14; The index is 4 for the formed and 0 for letter

6. The index for C7H7NO is 5 , and a possible structure is Of course, other isomers( compounds with the same molecular formula) are possible , such as Note that the benzene ring itself accounts for four “sites of unsaturation“ Three for the double bonds and one for the ring.

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