Question

What are the major differences you would see in the infrared spectra of an alkane, alkene, and alkyne?

Answer 1

Answer – We know the infrared spectra gives us the information about the functional group.

We also know the alkane has all single bond, alkene has double bond and alkyne has triple bond. IR showing the stretching frequency, so as the bond strong and shorter the IR stretching frequency is high and as the bond weak and longer the IR stretching frequency is less.

We know alkane have all single bonds and alkene has one double bond, so as the double bond increase means pi bond the bond gets shorter and strong, so the bond strong in alkyne then alkene and lastly alkane.

So the IR for the alkane C-C stretching and bending bands is at too low a frequency or very weak in the IR

For the alkene, C=C the IR frequency at 1600 to 1680 cm^-1

For the alkyne C triple bond C the IR frequency at 2100 to 2250 cm^-1

So the major differences see in the infrared spectra of an alkane, alkene, and alkyne in the stretching frequency.