Degree Of Unsaturation Worksheet With Answer Key (Page 2 of 6) in pdf

Degree Of Unsaturation Worksheet With Answer Key Page 2

Saturated vs. Unsaturated Molecules

In the lab,

saturation

may be thought of as the point when a solution cannot dissolve anymore of a substance added to it.

In terms of degrees of unsaturation, a molecule only containing single bonds with no rings is considered saturated.

chewiki_sat2

(3).bmp

chewiki_sat.bmp

1-methyoxypentane

Unlike saturated molecules, unsaturated molecules contain double bond(s), triple bond(s) and/or ring(s).

chewiki_unsat1.bmp chewiki_unsat2.bmp

chewiki_unsat3.bmp

3-chloro-5-octyne

CH=CHCH

Calculating Degrees of Unsaturation (DoU)

If the molecular formula is given, plug in the numbers into this formula:

\[ DoU= \dfrac{2C+2+N-X-H}{2} \]

• \(C\) 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

As stated before, a saturated molecule contains only single bonds and no rings. Another way of interpreting this

is that a saturated molecule has the maximum number of hydrogen atoms possible to be an acyclic alkane. Thus,

the number of hydrogens can be represented by 2C+2, which is the general molecular representation of an alkane. As

an example, for the molecular formula C

the number of actual hydrogens needed for the compound to be saturated

is 8 [2C+2=(2x3)+2=8]. The compound needs 4 more hydrogens in order to be fully saturated (expected number of

hydrogens-observed number of hydrogens=8-4=4). Degrees of unsaturation is equal to 2, or half the number of hydrogens

the molecule needs to be classified as saturated. Hence, the DoB formula divides by 2. The formula subtracts the number

of X's because a halogen (X) replaces a hydrogen in a compound. For instance, in chloroethane, C

Cl, there is one

less hydrogen compared to ethane, C

Degree Of Unsaturation Worksheet With Answer Key Page 2