How this calculator works
Double bond equivalent and degree of unsaturation are two names for the same count. Each ring or double bond contributes one; a triple bond contributes two. Oxygen does not alter the hydrogen deficiency. This valence model assumes neutral closed-shell CHNO/halogen compounds; it does not identify the positions of rings or bonds.
Formula
DBE = 1 + C + (N - H - X)/2, where X is the total halogen count.
Worked example
Benzene C6H6 gives 1 + 6 - 6/2 = 4. Ethene C2H4 gives 1 + 2 - 4/2 = 1.
Advertisement
Frequently asked questions
Does oxygen affect DBE?
No. Divalent oxygen leaves this hydrogen-deficiency count unchanged.
Can a DBE be half an integer?
A half-integer can indicate a radical, charge or unsuitable valence model. This tool rejects it for its neutral closed-shell model.
Can DBE reveal the structure?
It constrains possible rings and multiple bonds, but many isomers have the same DBE.