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Rate and equilibrium measurements have been obtained for the nitrosation (using nitrous acid in dilute acid aqueous solution) of the following thione-thiol nitrogen heterocyclic species and for the decomposition reactions of the formed S-NO ϩ ions: 4-mercaptopyridine (1), 2-mercaptopyridine 1-oxide (2), 2-mercaptopyrimidine (3) and 2-mercapto-1H-imidazole (4). The nitrosation reactions were all rapid and rate constants were obtained by stoppedflow spectrophotometry. In all cases kinetic analysis showed that the halide ion-catalysed and the uncatalysed reactions occurred at or close to the diffusion-controlled limit and the reactive form of the substrate is its thione form. In some cases at high [nitrous acid] reaction occurred via N 2 O 3 where the rate-limiting step is that of N 2 O 3 formation. Similarly reaction of 1 and 3 in the presence of thiocyanate showed that reaction takes place via ratelimiting formation of ONSCN. All of the nitrosation reactions were somewhat reversible, with large equilibrium constants of 2.0 × 10 7 , ~4 × 10 5 , 1.7 × 10 3 and 1.5 × 10 5 dm 6 mol Ϫ2 respectively for 1, 2, 3, and 4. All of the S-NO ϩ ions decomposed rapidly in solution generating the disulfides and nitric oxide. This reaction was monitored only for the S-NO ϩ derived from 1 and 2 because of stability problems. The deprotonated form of the S-nitroso product from 1 was identified from measurements at pH 7.4 and the pK a value of the protonated form estimated as 4.5. It decomposed fairly rapidly to give the thione. We report some results where thiones show considerable catalytic activity in nitrosation reactions of N-methylaniline and ascorbic acid.

Kinetic and equilibrium results are reported for the reactions of sulphite with the ethyl and phenyl ethers of 2,4,6-trinitrophenol and 2,4,6-trinitrothiophenol in 80/20 (v/v) water/DMSO. In each case 1:1 and 1:2 adducts are observed by reaction of sulphite at one or two unsubstituted ring positions respectively. In the case of the ethyl derivatives these adducts are long-lived; however, the phenyl derivatives rapidly yield 2,4,6-trinitrobenzenesulphonate, the substitution product. This difference is attributed to a change in the nature of the rate-determining step, from nucleophilic attack with the phenyl derivatives to leaving group departure with the alkyl derivatives.

Introduction/Purpose: Sedentary behavior (SB) is common in desk-based work, and prolonged periods of SB are associated with negative health outcomes. This study assessed associations between workplace characteristics and setting and movement patterns during working hours. Methods: This secondary analysis used baseline data from the Reducing Sedentary Behavior to Decrease Blood Pressure clinical trial, which enrolled inactive, desk-based workers with elevated blood pressure (n = 271; mean age, 45.3 ± 11.6 yr; body mass index, 30.66 ± 7.1 kg•m −2 ; 59.4% women). Physical and social workplace characteristics were assessed by a study-developed questionnaire and the Office Environment and Sitting Scale. Participants also wore an activPAL activity monitor for 7 d and reported working hours in a diary to measure SB and physical activity (PA) specifically while working. Linear regression was used to analyze cross-sectional associations between workplace characteristics and SB and PA. A stratified analysis was also conducted to assess associations among home-based and in-office desk workers separately. Analyses were adjusted for age, gender, body mass index, and work wear time. Results: Participants spent 77% of working hours in SB. Public versus private offices, working in-office versus at home, higher local connectivity, and greater overall connectedness were associated with lower SB and/or greater PA (all P < 0.05). Higher frequency of face-to-face interactions, and greater visibility and proximity to coworkers were associated with less SB and more PA (all P < 0.05). For example, home-based workers had more total SB (+17.2 ± 8.4 min per day), more SB bouts ≥30 min (+39.1 ± 12.8 min per day), and less steps (695 ± 201 steps per day) than in-office employees. Stratification by office setting revealed differences in associations between SB and PA and workplace characteristics. Conclusions:More public, open spaces with more social interactions and physical walkways could improve SB and PA patterns during work. Home-based workers had more SB, less PA, and unique associations of these activities with workplace characteristics, suggesting a need for tailored interventions.