An important specific rearrangement process in oxygenated organic compounds has been found to involve the formation of carbon monoxide. A combination of accurate mass measurement and metastable peak analysis has provided in many cases unequivocal information on the course of the fragmentation processes involved. A fairly detailed study of the fragmentation of anthraquinone has shown that fresh bonds are formed to produce the ionized forms of fluorenone and o-diphenylene; in the case of hydroxy derivatives of anthraquinone the ion CnH,+ appears to have high stability. Other compounds, mainly aromatic ethers and ketones, are discussed in a similar way and in a few cases suggestions are made regarding the nature of the transition states involved in these s ecific rearrangements. Analogously, HCN, NO and other groups are eliminated from nitrogen-containing compounds suct as the nitroanilines. The theoretical implications of such specific low energy processes are considered briefly, with reference to the quasi-equilibrium theory of mass spectra.

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The mechanism whereby neutral carbon monoxide is ejected from the ($-OH)+ ion from o-nitrotoluene under electron impact has been studied. The compound o-nitro[Me-13C] toluene was prepared in order to assist this study.

Ring Size upon thc! Stability of Metal Chelntes. 3495five-and six-membered rings. Supplemented by data in the literature, the results confirm the hypothesis that increase in chelate ring size is accompanied by a decrease in stability.From measurements at a series of temperatures it is possible to analyse the free-energy change of a chelation reaction into its component entropy and heat terms. The latter may also, with advantage, be determined by direct calorimetry. In a further paper (Irving and Dickens, in preparation) such thermodynamic data for many of the complexes referred to in this paper will be presented and discussed.Chelate Rings formed by Aliphatic Diamistes.--By the Calvin-B j errum technique as previously described (Irving and Griffiths,

Certain of the "meta-stable peaks" in mass spectra are abnormally wide. This extra width is shown to be associated with release of kinetic energy during fragmentation. Methods are presented for measuring this energy release and values are given for various transitions in the spectra of aromatic nitro compounds.Meta-stable ions are often detected in the mass spectra of organic compounds 1* 2. These ions may be detected if they dissociate near the entrance slit of the magnetic analyser in sector magnetic field mass spectrometers. If ions of original mass ml dissociate to produce ions of mass m,, a peak appears in the mass spectrum at a position m ' where m*==m,2/ml. (1)These peaks are usually quite small and are mu& broader than peaks produced by normal stable ions. They often extend over a range of several mass numbers and usually have a shape resembling a GAussian distribution curve. Their maxima are usually sufficiently well defined to enable one to determine the values of mi and m e , from equation ( l ) , for the ions involved in the transition. Occasionally, however, some of these "meta-stable peaks" are observed to be much broader than usuaI and to have a relatively flat top. Theoretical ConsiderationsIn arriving at the approximate relationship of equation (1) , HIPPLE and his co-workers assumed that there was a negIigible release of kinetic energy during the dissociation. In such a case the kinetic energy acquired by an ion of mass ml during the acceleration process is shared on dissociation between the two resulting particles in proportion to their masses.Let us now consider an ion mi+ which is formed in the ionization &amber with zero kinetic energy and falls through a potential Yl before dissociating into an ion m2+ and a neutral fragment (ml -m,) , i.