Colin G. Macdonald

1-Cyano-3,4-epithiobutane: A major product of glucosinolate hydrolysis in seeds from certain varieties of Brassica campestris

Abstract A new hydrolysis product derived from 3-butenylglucosinolate in seeds of certain strains of Brassica campestris Yellow Sarson is described. The structure, 1-cyano-3,4-epithiobutane is proposed. If the seeds are heated at 115° for 30 min before hydrolysis, 3-butenyl isothiocyanate is the main product.

An ambiguous assignment of a metastable peak for a sequential fragmentation process

Abstract The information obtained from two-dimensional spectra can be insufficient to distinguish metastable peaks for sequential processes from other peaks. The ion current attributed to the loss of Cl·. followed by CO from the metastable molecular ion of 3-chlorophenol in consecutive field-free regions of a double focussing mass spectrometer has been subjected to three-dimensional analysis. Any metastable peak for this process is obscured by a more intense ion current due to an unrelated reaction within the field of the electric sector.

Broadening effects on the mass resolution of metastable peaks

Abstract The mass resolution achieved for daughter ions resulting from metastable ion reactions in the first field-free region of a double-focussing mass spectrometer is less than that for the main-beam daughter ions. A Monte-Carlo computer program that simulates a mass spectrometer has been used to show that the occurrence of the reactions at points in the first field-free region other than at the fast-sector object slit can give rise to such broadening of the metastable peaks.

Analysis at high mass-resolution of metastable transitions in mass spectrometry

When the accelerating and electric sector voltages of a Nier–Johnson mass spectrometer are simultaneously varied to produce a spectrum of daughter ions derived from a selected metastable parent ion, the spectrum contains peaks which are not diffuse, so that precise mass measurement is facilitated and peaks due to isobaric daughter ions may be resolved.

Factors influencing the chelate linkage isomerism of some oxime complexes of nickel(II)

1 H N.m.r. and i.r. spectroscopy show that the (4-iminopentane-2,3-dione 3-oximato) ligand forms a five-membered chelate ring in (4-iminopentane-2,3-dione 3-oximato)(4-aminopent-3-en-2-onato)nickel(II) but a six-membered chelate ring in (3-methyliminobutan-2-one oximato)(4-iminopentane-2,3-dione 3-oximato)nickel(II). The stability of these and related mixed-ligand complexes of nickel(II) is attributed to the presence of intramolecular hydrogen bonding between the imino hydrogen atom of one ligand and the oximino oxygen atom of the other.