The effect of charge on hydroxyl loss from ortho-substituted nitrobenzene ions

✍ Scribed by Scott A. McLuckey; Gary L. Glish

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 466 KB
• Volume: 22
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210220409

✦ Synopsis

An abundant loss of hydroxyl in decompositions of ortho-substituted nitroarene cations is commonly observed when the substituent contains one or more labile hydrogen atoms. The major loss of hydroxyl also takes place from many but not all of the corresponding molecular anions. Data are reported for the collisionally activated decompositions of the cations and anions of o-nitrotoluene, o-nitrophenol and o-nitroaniline. Data for some dinitro ions are also reported. The results can be rationalized on the basis of a greater degree of charge developed at the substituent in the transition state of the anions that leads to a rearranged ion. It is from this structure that hydroxyl is lost via simple bond cleavage. This can be viewed most simply as a proton transfer from the substituent to the nitro group in the anion as opposed to hydrogen transfer in the analogous step for the cation. The degree to which hydroxyl loss occurs is therefore largely determined by the tendency for hydrogen (cations), or proton (anions), transfer from the substituent to the nitro group.