Degree of Unsaturation Explained | Rings, Double Bonds and Triple Bonds

How do you know whether an organic molecule contains rings, double bonds or triple bonds just from its molecular formula?

In this A-Level Chemistry video, we explain degree of unsaturation clearly. You will learn how D.U. counts the total number of rings and π bonds in a molecule, why any double bond counts as 1 D.U., why any triple bond counts as 2 D.U., and why a benzene ring has D.U. = 4.

We will use the shortcut formula:

D.U. = C − H/2 + 1

Before applying the formula:
• Halogen → count as H
• Nitrogen → subtract 1H
• Oxygen → ignore

You will also learn why cycloalkanes are saturated but still have D.U. = 1 because they contain one ring.

Examples covered:
• C₄H₈O₂
• C₃H₇Br
• C₆H₆
• C₃H₄
• C₃H₆O

By the end of this video, you should be able to:
• calculate degree of unsaturation from molecular formula
• explain what D.U. actually counts
• understand why rings contribute to D.U.
• recognise that any double bond gives 1 D.U.
• recognise that any triple bond gives 2 D.U.
• explain why benzene has D.U. = 4
• avoid the common mistake that “saturated” always means D.U. = 0

This video is useful for A-Level Chemistry, Singapore H2 Chemistry, organic chemistry, spectroscopy, proton NMR and structure elucidation revision.

Next video: How to interpret a proton NMR spectrum using molecular formula, degree of unsaturation, chemical shift, integration and splitting.

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Видео Degree of Unsaturation Explained | Rings, Double Bonds and Triple Bonds канала David Tan Chemistry