Editing Aldehyde (section)

==Physical properties and characterization==
Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes such as [[formaldehyde]] and [[acetaldehyde]] are soluble in water, and the volatile aldehydes have pungent odors.

Aldehydes can be identified by spectroscopic methods. Using [[IR spectroscopy]], they display a strong ''ν''<sub>CO</sub> band near 1700&nbsp;cm<sup>−1</sup>. In their [[Proton nuclear magnetic resonance|<sup>1</sup>H NMR]] spectra, the formyl hydrogen center absorbs near ''δ''<sub>H</sub>&nbsp;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&nbsp;Hz. The <sup>13</sup>C NMR spectra of aldehydes and ketones gives a suppressed (weak) but distinctive signal at ''δ''<sub>C</sub>&nbsp;190 to 205.