21620-60-0

In the present work, we have characterized in detail the chemical structures of secondary organic aerosol (SOA) components that were generated in a smog chamber and result from the photooxidation of isoprene under high-NO x conditions typical for a polluted atmosphere. Isoprene high-NO x SOA contains 2-methylglyceric acid (2-MG) and oligoester derivatives thereof. Trimethylsilylation, in combination with capillary gas chromatography (GC)/ion trap mass spectrometry (MS) and detailed interpretation of the MS data, allowed structural characterization the polar oxygenated compounds present in isoprene SOA up to 2-MG trimers. GC separation was achieved between 2-MG linear and branched dimers or trimers, as well as between the 2-MG linear dimer and isomeric mono-acetate derivatives thereof. The electron ionization (EI) spectra of the trimethylsilyl derivatives contain a wealth of structural information, including information about the molecular weight (MW), oligoester linkages, terminal carboxylic and hydroxymethyl groups, and esterification sites. Only part of this information can be achieved with a soft ionization technique such as electrospray (ESI) in combination with collision-induced dissociation (CID). The methane chemical ionization (CI) data were used to obtain supporting MW information. Interesting EI spectral differences were observed between the trimethylsilyl derivatives of 2-MG linear and branched dimers or trimers and between 2-MG linear dimer mono-acetate isomers. Copyright

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A simple two-step approach to methyltartronic acid (2-hydroxy-2-methylpropanedioic acid, 3) from methacrylic acid (1) via α-methylglyceric acid (2) is described. It is based on the successive use of hydrogen peroxide and oxygen as oxidants in the same aqueous medium, in combination with tungstic acid and palladium on carbon as catalysts, respectively.

SN2 and E2 competing reactions in cyclic sulfamidates can be modulated by the change of an amide group to an ester group attached to the quaternary carbon activated for the nucleophilic attack, allowing an easy approach to enantiopure α,α-disub

There is described a process for preparing alkyl esters of methyltartronic acid by hydroxylation of methacrylic acid to alpha-methylglyceric acid with H2 O2, in an aqueous medium, in the presence of H2 WO4 and optionally of H3 PO4 or H3 AsO4 or alkaline salts thereof as catalysts, at pH3 in excess or with O2, in an aqueous-alkaline medium, in the presence of Pd or Pt carried on carbon or oxides thereof as catalysts, at temperatures of 60°-100° C., and final esterification of methyltartronic acid with alcohols C1 -C4.

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