How do you interpret FTIR peaks?

Once the initial testing and spectrum collection is complete, interpretation of FTIR spectra comes next. Typically, interpreting FTIR spectra starts at the high frequency end to identify the functional groups present. The fingerprint regions are then studied to positively identify the compound.

What does IR peak at 3000 mean?

Absorption peaks above 3000 cm-1 are frequently diagnostic of unsaturation. Alkynyl C-H Stretch. Alkynyl C=C Stretch.

Why is the OH peak broad?

At moderate concentrations the O-H stretch appears both as a sharp, weak peak at 3600-3500 cm-1 and a strong, broad peak at 3400-3200 cm-1. Hydrogen-bonded O-H stretches are much broader because the hydrogen bonds vary in strength.

What does a broad peak mean in IR?

A very broad peak in the region between 3100 and 3600 cm-1 indicates the presence of exchangeable protons, typically from alcohol, amine, amide or carboxylic acid groups (see further discussion of this below).

What is the range of IR peak cm-1 of sp3 C-H bond?

between 2800 and 3300 cm-1
Hydrocarbons show IR absorption peaks between 2800 and 3300 cm-1 due to C-H stretching vibrations. The hybridization of the carbon affects the exact position of the absorption — stiffer bonds vibrate at higher frequencies. sp3 C-H: 2800-3000, sp2 C-H: 3000-3100, sp C-H: 3300 cm-1.

What is C-H stretching and bending?

Alkenes The vinylic hydrogen (=C-H) stretches appear just above 3000 cm-1; they overlap the aromatic C-H stretches. The C=C stretch is medium to non- existent between 1640 and 1670 cm-1. The most characteristic vibrational modes of alkenes are the out-of-plane C-H bending vibrations between 650 and 1000 cm-1.

Why IR peaks are sharp?

The sharpness or broadness of a stretch in IR spectra depends on extent of Hydrogen bonding present in the molecule. Basically, if it undergoes immense intermolecular hydrogen bonding, the peaks tend to be broader and the lesser the hydrogen bonding becomes, the sharper the peaks get in the spectra.