Ion-molecule reactions ionization

Jennings and coworkers " were the first to report on a mass spectrometric method of locating double bonds by use of gas-phase ion/molecule reactions. Ionized alkyl vinyl ethers proved to be highly suitable reagent ions, and the principle of this gas-phase method for double-bond localization is illustrated for prototype dienes 76-78 in Scheme 22. At the same time. Hunt and coworkers introduced nitric oxide (NO) as a reagent gas in Cl mass spectrometry and studied the reactions of the NO+ and [NONO]+ ions with alkenes and also with several acyclic dienes and 1,3,5-cycloheptatriene. Thereafter, several groups have contributed to the development and only some classical work concerning simple alkenes may be mentioned here. 

High-pressure mass spectrometry has been studied for many years by workers interested in ion-molecule reactions. Ionization of the substance under scrutiny is affected by reactions between the molecules of the compound and a set of ions that serve as ionizing reactants. The reactant ions are formed by subjecting a gas to electron bombardment at pressures of about 1 mm. The reactant gas is extensively ionized and, because of the high pressure, undergoes ion molecule reactions with itself and with the sample molecules that are present at relatively low concentrations (less than 1 percent. This process in a mass spectrometer is termed chemical ionization CCI). 

---