Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors.
Aldehydes can be identified by spectroscopic methods. Using IR spectroscopy, they display a strong ν band near 1700 cm. In their H NMR spectra, the formyl hydrogen center absorbs near δ 9.5 to 10, which is a distinctive part of the spectrum. This signal shows the characteristic coupling to any protons on the α carbon with a small coupling constant typically less than 3.0 Hz. The C NMR spectra of aldehydes and ketones gives a suppressed (weak) but distinctive signal at δ 190 to 205.