We’re being asked to **determine the index of hydrogen deficiency (IHD)** for **C _{5}H_{6}F_{3}N**.

Recall that the ** degrees of unsaturation** or

For a given molecular formula, the IHD is calculated using:

$\overline{){\mathbf{IHD}}{\mathbf{=}}\frac{[2n+2]\mathbf{-}\mathbf{H}}{\mathbf{2}}}$

where **n = number of carbons** and **H** is:

• **+1** for *hydrogen (H) or halogens (X)*

• **0** for *oxygen (O)*

• **–1** for *nitrogen (N)*

How many degrees of unsaturation are in a compound with the formula C_{5}H_{6}F_{3}N?