In other words, a saturated form of a hydrocarbon will have the maximum number of hydrogen atoms in an acyclic alkane form. The reason that the value of halogen atoms X is subtracted is because it replaces an equal number of hydrogen i.
Apart from that, nitrogen brings in more hydrogen atoms and because of that the value is added. Oxygen and Sulphur do not seem to have any effect in changing the saturation status of a compound. The information obtained from the degree of unsaturation can be characterized as: 1 value of DU gives 1 ring or 1 double bond. For a triple bond, 2 is the minimum DU value. The following two simple examples will illustrate the use and understanding of how to find the degree of unsaturation and the degree of unsaturation formula.
Example 1: For a compound having the molecular formula C 3 H 4 , find the degree of unsaturation. Solution: The given formula is C 3 H 4. Since there is no nitrogen or halogen the degree of unsaturation formula is reduced to:. Hence, this number is 8. Thus, the molecule needs 4 more hydrogen atoms to be saturated.
For a compound to be saturated, there is one more hydrogen in a molecule when nitrogen is present. Therefore, we add the number of nitrogens N. Oxygen and sulfur are not included in the formula because saturation is unaffected by these elements. As seen in alcohols, the same number of hydrogens in ethanol, C 2 H 5 OH, matches the number of hydrogens in ethane, C 2 H 6.
Each row corresponds to a different combination. This corresponds to benzene containing 1 ring and 3 double bonds. However, when given the molecular formula C 6 H 6 , benzene is only one of many possible structures isomers. The following structures all have DoB of 4 and have the same molecular formula as benzene.
However, you can also determine the molecular formula and solve for the degrees of unsaturation by using the formula. Thus, the formula may give numerous possible structures for a given molecular formula. 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. There are many ways one can go about determining the structure of an unknown organic molecule. Although, nuclear magnetic resonance NMR and infrared radiation IR are the primary ways of determining molecular structures, these techniques require expensive instrumentation and are not always readily available.
Fortunately, calculating the degrees of unsaturation provides useful information about the structure. The degree of unsaturation indicates the total number of pi bonds and rings within a molecule which makes it easier for one to figure out the molecular structure. The molecular formula of a hydrocarbon provides information about the possible structural types it may represent. 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. As an example, for the molecular formula C3H4 the number of actual hydrogens needed for the compound to be saturated is 8. 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.
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