A Novel,Efficient Synthesis of 3,3-Dimethylindoline

The Lewis acid mediated cyclisation of N-methallylacetanilide, followed by hydrolysis to give 3,3-dimethylindoline in excellent yield is described.     

Concealed Cyclotrimeric Polymorph of Lithium 2,2,6,6‐Tetramethylpiperidide Unconcealed: X‐Ray Crystallographic and NMR Spectroscopic Studies

Lithium 2,2,6,6‐tetramethylpiperidide (LiTMP), one of the most important polar organometallic reagents both in its own right and as a key component of ate compositions, has long been known for its classic cyclotetrameric (LiTMP)₄ solid‐state structure. Made by a new approach through transmetalation of Zn(TMP)₂ with tBuLi in n‐hexane solution, a crystalline polymorph of LiTMP has been uncovered. X‐ray crystallographic studies at 123(2) K revealed this polymorph crystallises in the hexagonal space group P6₃/m and exhibited a discrete cyclotrimeric (C_3h) structure with a strictly planar (LiN)₃ ring containing three symmetrically equivalent TMP chair‐shaped ligands. The molecular structure of (LiTMP)₄ was redetermined at 123(2) K, because its original crystallographic characterisation was done at ambient temperature. This improved redetermination confirmed a monoclinic C2/c space group with the planar (LiN)₄ ring possessing pseudo (non‐crystallographic) C_4h symmetry. Investigation of both metalation and transmetalation routes to LiTMP under different conditions established that polymorph formation did not depend on the route employed but rather the temperature of crystallisation. Low‐temperature (freezer at ?35 °C) cooling of the reaction solution favoured (LiTMP)₃; whereas high‐temperature (bench) storage favoured (LiTMP)₄. Routine ¹H and ¹³C NMR spectroscopic studies in a variety of solvents showed that (LiTMP)₃ and (LiTMP)₄ exist in equilibrium, whereas ¹H DOSY NMR studies gave diffusion coefficient results consistent with their relative sizes.     

Solvent‐Driven Reductive Activation of CO2 by Bismuth: Switching from Metalloformate Complexes to Oxalate Products

In this work, we investigated how the reductive activation of CO₂ with an atomic bismuth model catalyst changes under aprotic solvation. IR photodissociation spectroscopy of mass‐selected [Bi(CO₂)_n]^? cluster ions was used to follow the structural evolution of the core ion with increasing cluster size. We interpreted the IR spectra by comparison with density‐functional‐theory calculations. The results show that CO₂ binds to a bismuth atom in the presence of an excess electron to form a metalloformate ion, BiCOO^?. Solvation with additional CO₂ molecules leads to the stabilization of a bismuth(I) oxalate complex and results in a core ion switch.     

Fundamentals of corrosion fouling

This paper reviews the fouling of heat transfer surfaces due to corrosion as a consequence of their exposure to flowing oxygenated water. The fundamental mechanisms of oxygen transport, deposit growth, and deposit removal are considered. A model for predicting the formation of a corrosion fouling deposit is derived, and the utility of dimensionless variables deduced from the model is demonstrated. The interaction of corrosion fouling and other categories of fouling is discussed. Recommendations are made for future research in this area.     

On the Spectrum of Steiner (v,k,t) Trades (II)

 A (v,k,t) trade T=T ₁−T ₂ of volume m consists of two disjoint collections T ₁ and T ₂ each containing m blocks (k-subsets) such that each t-subset is contained in the same number of blocks in T ₁ and T ₂. If each t-subset occurs at most once in T ₁, then T is called a Steiner (k,t) trade. In this paper, we continue our investigation of the spectrum S(k,2); that is, the set of allowable volumes of Steiner (k,t) trades when t=2. By using the concept of linked trades, we show that 2k+1∈S(k,2) precisely when k∈{3, 4, 7}. Received: February 28, 1997     

Some cross-sections for the photo-production of neutral Pi-mesons from hydrogen at energies from 360 to 938 MeV

Some cross-sections for the photo-production ofπ ⁰-mesons from hydrogen for pion c.m. angles in the range 60°–125° are presented. The data have been obtained by measuring proton yields from a hydrogen target, thus permitting separation of single-pion production from the strong background caused by double-pion production. The values, which extend from 360 to 938 MeV, show reasonable agreement with the results of a recent phase-shift analysis.     

Development of an electrochemical method for the rapid determination of microbial concentration and evidence for the reaction mechanism

A rapid amperometric method for the determination of microbial concentration is described. The micro-organisms reduce the redox mediator, potassium hexacyanoferrate(III), which is reoxidized to yield a current proportional to the microbial concentration. Escherichia coli gave a linear response (standard error (S_YX)=0.17, r=0.9999, n=5, P>99.9%) over the concentration range 10⁶–10⁸ cells ml^?1 with a response time of less than 1 min. The effect of varying temperature showed that the electrochemical response of the bacteria was linked to respiration rate. Studies with respiratory inhibitors suggested that hexacyanoferrate (III) is reduced by the segment of the respiratory chain between nicotinamide adenine dinucleotide (NADH) dehydrogenase and the terminal oxidases.