title: Mechanistic study of maleic anhydride grafting onto fatty double bonds using mass spectrometry.
abstract: BACKGROUND
  The grafting of maleic anhydride onto fatty C=C double bonds is a well-known and used method to functionalize triglyceride molecules. Nevertheless, grafted products are not actually structurally well defined. In this work, the thermal grafting of maleic anhydride onto (un)saturated fatty acid esters without the use of an initiator was characterized in order to determine the nature of the products formed during this reaction.
  
  
  METHODS
  Complementary spectrometric techniques, ESI-MS(n) (ion-trap mass spectrometer), IMS-MS(n) (Q-IMS-TOFMS) and GC/MS, were used to identify the grafted products which were prepared using either ethyl oleate (EtO) or methyl linoleate (MeL) as model molecules and maleic anhydride (MA). Lithiated adducts were investigated since they yield useful structural information when subjected to collision-induced dissociation (CID) in tandem mass spectrometry.
  
  
  RESULTS
  A high number of products are formed during MA grafting and various reaction types could occur. Radical addition of maleic anhydride followed by combination or elimination reactions led to succinic and maleic anhydride grafting, respectively. The addition occurred with or without double-bond shift; the resulting derivatives showed succinic and maleic anhydride branching in the α-position relative to the double bond or onto the carbon atom of the initial double bond. Some structures obtained by radical addition and combination were also consistent with the Alder ene functionalization reaction. The Diels-Alder addition between di-unsaturated fatty acid chains and maleic anhydride could yield cyclic forms of MA-grafted derivatives.
  
  
  CONCLUSIONS
  We have shown that ESI-MS(n) and IMS-MS(n) allow the identification of grafted products providing relevant structural information concerning isomers. These methods permit the rapid and direct analyses of 'crude reaction mixtures'.
authors.affiliation: Université de Rouen, Laboratory COBRA UMR 6014 & FR 3038, IRCOF, 1 Rue Tesnière, 76821 Mont St Aignan Cedex, France. Corinne.Loutelier@univ-rouen.fr
authors.forename: Corinne
authors.initials: C
authors.lastname: Loutelier-Bourhis
authors.forename: Ornella
authors.initials: O
authors.lastname: Zovi
authors.forename: Laurence
authors.initials: L
authors.lastname: Lecamp
authors.forename: Claude
authors.initials: C
authors.lastname: Bunel
authors.forename: Marie
authors.initials: M
authors.lastname: Hubert-Roux
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Lange
mesh_terms: D055598:Chemical Phenomena; D005227:Fatty Acids / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D008041:Linoleic Acids / Q000737:chemistry; D008299:Maleic Anhydrides / Q000737:chemistry*; D008958:Models, Molecular; D009829:Oleic Acids / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013229:Stearic Acids / Q000737:chemistry
chemical_list: D005227:Fatty Acids; D008041:Linoleic Acids; D008299:Maleic Anhydrides; D009829:Oleic Acids; D013229:Stearic Acids; C005575:methyl linoleate; C031183:stearic acid; C033180:ethyl oleate