Methyl thiocyanate

Abstract: Infection by Pseudomonas aeruginosa (PA) is a major cause of morbidity and mortality in patients with cystic fibrosis (CF). Breath analysis could potentially be a useful diagnostic of such infection, and analyses of volatile organic compounds (VOCs) emitted from PA cultures are an important part of the search for volatile breath markers of PA lung infection. Our pilot experiments using solid-phase microextraction, SPME and gas chromatography/mass spectrometric (GC/MS) analyses of volatile compounds produced by PA strains indicated a clear presence of methyl thiocyanate. This provided a motivation to develop a method for real-time online quantification of this compound by selected ion flow tube mass spectrometry, SIFT-MS. The kinetics of reactions of H3O+, NO+ and O2+• with methyl thiocyanate at 300 K were characterized and the characteristic product ions determined (proton transfer for H3O+, rate constant 4.6 × 10–9 cm3 s–1; association for NO+, 1.7 × 10–9 cm3 s–1 and nondissociative charge transfer for O2+•, 4.3 × 10–9 cm3 s–1). The kinetics library was extended by a new entry for methyl thiocyanate accounting for overlaps with isotopologues of hydrated hydronium ions. Solubility of methyl thiocyanate in water (Henry's law constant) was determined using standard reference solutions and the linearity and limits of detection of both SIFT-MS and SPME-GC/MS methods were characterized. Thirty-six strains of PA with distinct genotype were cultivated under identical conditions and 28 of them (all also producing HCN) were found to release methyl thiocyanate in headspace concentrations greater than 6 parts per billion by volume (ppbv). SIFT-MS was also used to analyze the breath of 28 children with CF and the concentrations of methyl thiocyanate were found to be in the range 2–21 ppbv (median 7 ppbv). Copyright © 2011 John Wiley & Sons, Ltd.

Abstract: 1,3-Dienyl ethers and the corresponding sulfides (CH2CHCHCHXR; XO, S; Ralkyl, phenyl) are readily metallated at C-1, using n-butyllithium and KO-t-Bu in tetrahydrofuran. 2H-Thiopyran can be lithiated at the 6-position with n-butyllithium and tetramethylethylenediamine in tetrahydrofuran. The various metallated compounds react smoothly with methyl iodide, methyl thiocyanate and acetaldehyde to give the expected derivatives. At about −20° a more than 95 % transformation of the metallated compound from cisCH2CHCHCHStBu into the trans-isomer occurs; with smaller R groups (isopropyl or ethyl) a less complete inversion is observed.

Abstract: Negative chemotaxis, the movement of organisms away from chemicals, was investigated in Pseudomonas aeruginosa using a rapid videotape method. Digital image processing was used to detect changes in bacterial numbers near the mouth of a capillary containing a test chemical. P. aeruginosa was found to be repelled by thiocyanic and isothiocyanic esters including allyl isothiocyanate, ethyl thiocyanate, methyl isothiocyanate and methyl thiocyanate. Particularly, the movement of bacteria away from methyl thiocyanate was so drastic that bacterial numbers near the mouth of the capillary decreased by approximately 80% within 30 s after the start of observation. Mutant strains, fully motile but lacking positive chemotaxis, did not escape away from the esters, suggesting a common mechanism between positive and negative chemotaxes in this organism.