Hydridic reactivity of W(CO)(H)(NO)(PMe3)(3) - Dihydrogen bonding and H-2 formation with protic donors

The hydridic reactivity of the complex W(CO)(H)(NO)(PMe3)(3) (1) was investigated applying a variety of protic donors. Formation of organyloxide complexes W(CO)(NO)(PMe3)(3)(OR) (R = C6H5 (2), 3,4,5-Me3C6H2 (3), CF3CH2 (4), C6H5CH2 (5), Me (6) and iPr (7)) and H-2 evolution was observed. The reactions of 1 accelerated with increasing acidity of the protic donor: Me2CHOH (pK(a) = 17) < MeOH (pK(a) = 15.5) < C6H5CH2OH (pK(a) = 15) < CF3CH2OH (pK(a) = 12.4) < C6H2Me3OH (pK(a) = 10.6) < C6H5OH (pK(a) = 10). Regioselective hydrogen bonding of 1 was probed with two of the protic donors furnishing equilibrium formation of the dihydrogen bonded complexes ROH center dot center dot center dot HW(CO)(NO)(PMe3)(3) (R = 3,4,5-Me3C6H2, 3a and iPr, 7a) and the O-NO hydrogen bonded species ROH center dot center dot center dot ONW(CO)(H)(PMe3)(3) (R = C6H2Me3, 3b and iPr, 7b) which were studied in hexane and d(8)-toluene solutions using variable temperature IR and NMR spectroscopy. Quantitative IR experiments at low temperatures using 3,4,5-trimethylphenol (TMP) confirmed the two types of competitive equilibria: dihydrogen bonding to give 3a (Delta H-1 = -5.8 +/- 0.4 kcal/mol and Delta S-1 = -15.3 +/- 1.4 e.u.) and hydrogen bonding to give 3b (Delta H-2 = -2.8 +/- 0.1 kcal/mol and Delta S-2 = -5.8 +/- 0.3 e.u.). Additional data for the hydrogen bonded complexes 3a,b and 7a,b were determined via NMR titrations in d(8)-toluene from the equilibrium constants K-(Delta delta) and K-(Delta R1) measuring either changes in the chemical shifts of H-W((Delta delta)) or the excess relaxation rates of H-W (Delta R-1) (3a,b: Delta H-(Delta delta) = -0.8 +/- 0.1 kcal/mol; Delta S-(Delta delta) = -1.4 +/- 0.3 e.u. and Delta H-(Delta R1) = -5.8 +/- 0.4 kcal/mol; Delta S-(Delta R1) = -22.9 +/- 1.9 e.u) (7a,b: Delta H-(Delta delta) = -2.3 +/- 0.2 kcal/mol; Delta S-(Delta delta) = -11.7 +/- 0.9 e.u. and Delta H-(Delta R1) = -2.9 +/- 0.2 kcal/mol; Delta S-(Delta R1) = -14.6 +/- 1.0 e.u). Dihydrogen bonding distances of 1.9 angstrom and 2.1 angstrom were derived for 3a and 7a from the NMR excess relaxation rate measurements of H-W in d(8)-toluene. An X-ray diffraction study was carried out on compound 2. (C) 2009 Elsevier B.V. All rights reserved

Calcium oxide as a promising heterogeneous catalyst for biodiesel production: Current state and perspectives

The present paper is an overview of the recent progress in the development of various CaO-based catalysts suitable for biodiesel production. The mechanism, kinetics and optimization of transesterification reaction over these catalysts are first considered. Then, the practical application of CaO-based catalysts is discussed with a special stress on leaching and reusability of these catalysts. Also, various continuous reactor systems currently in use for biodiesel production are appraised. In addition to it, purification of crude biodiesel and the ecological aspects of using CaO-based catalysts are considered. Finally, the potentials of CaO-based catalysts for heterogeneous catalysis for biodiesel production are emphasized to assess the future perspectives of their use. This review might help in selecting suitable CaO-based catalysts and the optimum reaction conditions for biodiesel production

New hepatitis C virus infection, re-infection and associated risk behaviour in male Irish prisoners: a cohort study, 2019

Abstract Background Prisoners are recognised as a high-risk population and prisons as high-risk locations for the transmission of hepatitis c virus (HCV) infection. Injecting drug use (IDU) is the main driver of HCV infection in prisoners and harm reduction services are often suboptimal in prison settings. HCV prevalence and incident data in prisoners is incomplete which impacts the public health opportunity that incarceration provides in identifying, treating and preventing HCV infection. The aim of this study is to identify new HCV infection and associated risk factors in an Irish male prison. Methods We conducted a follow up (18-month) cohort study on prisoners who had previously tested negative, self-cleared or had been successfully treated for HCV infection. We conducted the study in a male medium security prison located in Dublin Ireland (Mountjoy Prison) using HCV serology, a review of medical records and a researcher-administered questionnaire. Results 99 prisoners with a mean age of 33.2 yrs. participated in the study and 82(82.8%) completed a research-administered questionnaire. Over half (51%) had a history of drug use from a young age (14.8 yrs.), 49.9% a history of heroin use and 39% a history of IDU. The prevalence of HIV and hepatitis B virus core antibody was 3% and HCV antibody was 22.2%. No new HCV infections were identified in those who had never been infected (n = 77), had self-cleared (n = 9) or achieved sustained virological response (n = 12). Small numbers of prisoners continued to engage in risk-behaviour including, IDU both in the prison (n = 2) and the community (n = 3), sharing syringes (n = 1) and drug taking paraphernalia (n = 6) and receiving non-sterile tattoos (n = 3). Conclusion Despite the high numbers of Irish prisoners with a history of IDU and HCV infection, new HCV infection is low or non-existent in this population. Small numbers of prisoners continue to engage in risk behaviour and larger studies are required to further understand HCV transmission in this cohort in an Irish and international context