The structure of an organic molecule is usually determined using spectroscopic methods, including mass spectrometry and infrared spectroscopy. The ionized sample molecule is called the molecular ion, M + , and measurement of its mass gives the molecular weight of the sample.

Finding the structure of a new molecule, whether a small one synthesized in the laboratory or a large protein found in living organisms, is central to the progression of chemistry and biochemistry. Mass spectrometry (MS) tells the molecular weight and formula of a molecule; infrared (IR) spectroscopy identifies the functional groups present in the molecule

structure of an organic molecule — usually determined using spectroscopic methods, including mass spectrometry and infrared spectroscopy. ionized sample molecule — called the molecular ion, M + , and measurement of its mass gives the molecular weight of the sample.