The breakdown of stainless steels in strong acids

A study was made of the corrosion behaviour in the ASTM standard Nitric acid and Oxalic acid tests, of two commercial AISI type 304L steels in the as received condition and after various heat treatments. Optical microscopy and SEM, TEM and STEM in conjunction with energy dispersive x-ray analysis, were used to correlate the corrosion behaviour of these steels with their microstructure. Some evidence of phosphorus segregation at grain boundaries was found. The corrosion behaviour at microstructural level was studied by examining on the TEM thin foils of steel that had been exposed to boiling nitric acid. Banding attack in the nitric acid and oxalic acid tests was studied using SEM and EPNA and found to be due to the micro-segregation of chromium and nickel. Using two experimental series of 304L, one a 17% Cr, 91 Ni, steel with phosphorus additions from 0.006% to 0.028%, the other a 20% Cr, 121 Ni steel with boron additions from 0.0011 to 0.00B51. The effect of these elements on corrosion in the nitric acid test was studied. The effect of different cooling rates and different solution treatment temperature on the behaviour of these steels was examined. TEM and STEM in conjunction with energy-dispersive x-ray analysis were again used to study the microstructure of the steels. Phosphorus was found to affect the corrosion behaviour but no effect was found with boron

Land use not litter quality is a stronger driver of decomposition in hyperdiverse tropical forest

Funded by Natural Environment Research Council. Grant Number: NE/K016253/1Peer reviewedPublisher PD

Investigation of the Deprotonative Generation and Borylation of Diamine-Ligated α-Lithiated Carbamates and Benzoates by in situ IR spectroscopy

Diamine-mediated α-deprotonation of <i>O</i>-alkyl carbamates or benzoates with alkyllithium reagents, trapping of the carbanion with organoboron compounds, and 1,2-metalate rearrangement of the resulting boronate complex are the primary steps by which organoboron compounds can be stereoselectively homologated. Although the final step can be easily monitored by ¹¹B NMR spectroscopy, the first two steps, which are typically carried out at cryogenic temperatures, are less well understood owing to the requirement for specialized analytical techniques. Investigation of these steps by in situ IR spectroscopy has provided invaluable data for optimizing the homologation reactions of organoboron compounds. Although the deprotonation of benzoates in noncoordinating solvents is faster than that in ethereal solvents, the deprotonation of carbamates shows the opposite trend, a difference that has its origin in the propensity of carbamates to form inactive parasitic complexes with the diamine-ligated alkyllithium reagent. Borylation of bulky diamine-ligated lithiated species in toluene is extremely slow, owing to the requirement for initial complexation of the oxygen atoms of the diol ligand on boron with the lithium ion prior to boron–lithium exchange. However, ethereal solvent, or very small amounts of THF, facilitate precomplexation through initial displacement of the bulky diamines coordinated to the lithium ion. Comparison of the carbonyl stretching frequencies of boronates derived from pinacol boronic esters with those derived from trialkylboranes suggests that the displaced lithium ion is residing on the pinacol oxygen atoms and the benzoate/carbamate carbonyl group, respectively, explaining, at least in part, the faster 1,2-metalate rearrangements of boronates derived from the trialkylboranes

Historic landscape management: a validation of quantitative soil thin-section analyses

The archaeological interpretation of past land management practices can be greatly enhanced through examination of soil thin sections. Features relating to manuring practice are among those key to interpreting agricultural practices. The sources and the pro¬cesses leading to the distribution of these manure materials may further improve knowledge of the past landscape utilisation. The use of quantitative analyses to examine soil thin sections opens the possibility of considering these relationships between manured areas in greater detail and to extract more subtle spatial and temporal changes in past management. In this study the validation of this methodology has been tested with quantitative image analysis methods used to examine manure inputs to a well-documented historical landscape of Papa Stour, Shetland, where intensive manuring has been practised until the 1960s. By using both historic and ethnographic evidence to validate the image analysis protocol, differences in spatial and temporal distribution are examined for the practices of manuring with both fuel residues and with turf. The validation of the hypotheses expected from ethnographic and historical data that quantitative soils-based evidence allows the definition of variations in manuring strategies and provides a more secure basis from which to interpret manuring management strategies in archaeological landscapes

Regioselective lithiation and electrophilic quench of N‐Boc‐3‐phenyltetrahydroisoquinoline

Tetrahydroisoquinolines are found in many natural products and drug compounds and a convenient method to access 1‐substituted derivatives is to carry out the lithiation at C‐1 followed by trapping with an electrophile. Here we explore the feasibility of lithiation at C‐3 by using a substrate with a benzylic proton on both sides of the nitrogen atom such that lithiation with nBuLi could occur at either C‐1 or C‐3 of the tetrahydroisoquinoline. The regioselectivity in the lithiation was determined using the substrate N‐tert‐butoxycarbonyl (Boc)‐3‐phenyltetrahydroisoquinoline. The lithiation could be followed by in situ ReactIR spectroscopy and the rate of rotation of the carbamate group was determined (barrier to rotation was approximately ΔG‡ 58 kJ/mol at –50 °C). Subsequent trapping of the organolithium species with an electrophile gave a mixture of two regioisomeric products with a preference for reaction at C‐1. This led to the isolation of 1,3‐disubstituted tetrahydroisoquinolines with trans relative stereochemistry. Removal of the Boc group from the nitrogen atom gave secondary and tertiary amine products