How does one determine whether double or triple bonds exist within a molecule?

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ncchemist | eNotes Employee

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The easiest way to determine whether double or triple bonds are present in a chemical is to use spectroscopic methods.  NMR, in particular, is very useful for identifying double bonds.  You see peaks in a proton NMR spectrum between 5 and 6 pm that are indicative of hydrogens attached to a carbon carbon bond.  If the chemical contains a carbon carbon triple bond with a hydrogen attached, a singlet will appear around 3 to 3.5 ppm.  If spectroscopic methods are not available, you can also use chemical reactions to determine if carbon carbon double or triple bonds are present.  Iodine, for example, readily adds to carbon carbon multiple bonds.  Since iodine is darkly colored if you add some to a chemical and the dark color disappears, then you can surmise that the iodine is being consumed by reacting with double and triple bonds.

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