Input
Result
Example Formulas
These examples demonstrate typical results. Parse and compute DBE using the same formula as the calculator.
| # | Formula | C | H | N | X (F+Cl+Br+I) | DBE |
|---|
Formula Used
The degree of unsaturation (DBE), also called the index of hydrogen deficiency, counts rings plus multiple bonds. For a composition containing C, H, N, and halogens X (F, Cl, Br, I):
DBE = (2 × C + 2 + N − H − X) ÷ 2
- Halogens are counted as hydrogen equivalents (included in X).
- Nitrogen adds one to the numerator (because a trivalent atom increases the hydrogen allowance by one).
- Oxygen and sulfur are ignored in the DBE calculation.
- Phosphorus is often treated like nitrogen; enable the option above if desired.
How to Use this Calculator
- Option A: Enter a molecular formula and click Parse Formula → Counts. The element counters will populate automatically.
- Option B: Type the atom counts for C, H, N, halogens, and optionally P. Toggle "Treat P as N" as needed.
- Press Calculate to compute the DBE. A message will flag non‑integer values (which can indicate radicals or an inconsistent formula).
- Use the Download buttons to export a CSV or PDF of the current result, or the examples table.
Tip: Common patterns — DBE of 4 often indicates an aromatic ring (one ring + three π bonds). DBE of 1 can be a ring or a double bond.
FAQs
1) What does a DBE value represent?
DBE equals the total number of rings plus π bonds in a structure. For example, a ring with three double bonds gives DBE = 4.
2) Why are oxygen and sulfur ignored?
They are typically divalent and do not change the hydrogen allowance in the saturated reference formula; including them would not affect DBE.
3) How are halogens handled?
Halogens (F, Cl, Br, I) are treated as hydrogen equivalents; subtract their total from the hydrogen count in the numerator.
4) What about phosphorus and other heteroatoms?
Phosphorus is commonly treated like nitrogen in DBE. Toggle the option if your convention requires it. Other heteroatoms are usually accounted for by valence considerations or ignored like oxygen.
5) The DBE is not an integer. What does that mean?
Non‑integer DBE values can indicate radicals, ionic formulas that exclude counterions, or an inconsistent empirical composition. Double‑check your counts.
6) Does charge change DBE?
In practice DBE counts rings and π bonds, which are independent of formal charge. However, ionic formulas may produce non‑integer results if counterions are omitted. In such cases, interpret cautiously.