Leaving Groups or Leaving Nucleophiles

Double Bond Equivalent or Degree of Unsaturation

The double bond equivalent (DBE) or degree of unsaturation is the rings plus the total number of multiple bonds. DBE is also known as index of hydrogen deficiency (IHD). The double bond equivalent can be calculated by using the formula is given below

Double Bond Equivalent (DBE) = (2C + 2 + N − X − H) / 2
Remember that the presence or absence of oxygen in an organic molecule does not impact the DBE value.
where, C is the number of carbons
N is the number of nitrogens
X is the number of halogens (F, Cl, Br, I)
H is the number of hydrogens

Calculate the degree of unsaturation for benzene.

The molecular formula for benzene is C₆H₆.
Thus, C = 6, N = 0, X = 0, and H = 6
Substituting the values in the formula we get
Degree of Unsaturation =2(6) + 2 − 6 / 2 = 4
Therefore, Degree of Unsaturation = 4

Calculate the double bond equivalent in glucose.

Molecular formula of glucose is C₆H₁₂O₆
From formula, DBU = [(2 x 6) + 2 − 12] / 2 = 1

What is the DBE value for lysine?

Molecular formula of lysine is C₆H₁₄N₂O₂
From formula, DBU = [(2 x 6) + 2 + 2 − 14] / 2 = 1

Caculate the double bond equivalent (degree of unsaturation) in compound (A)

H₂/Pt causes the catalytic hydrogenation of alkenes. Since 1 mole of the reagent is used, therefore, it will bring about the addition of H₂ at one double bond only. So, in the compound A, two cyclopentane rings are should be present along with a double bond. Due to the presence of two rings and one double bond in A its double bond equivalent is 3. We can also calculate it using the formula.