[{LiCH(CH2CH2OMen)SO2Ph}4] (OMen = Menthyl): Synthesis and First Structure of a Chiral Solvent Free Lithiated Sulfone with a Direct Li–C Bond

R*OCH₂CH₂CH₂SO₂Ph (R*OH = MenOH, (–)‐menthol, ( 3a ); BorOH, (1S)‐(–)‐borneol, ( 3b )) were found to react with n‐BuLi in n‐pentane/n‐hexane and toluene/n‐hexane under deprotonation yielding LiCH(CH₂CH₂OR*)SO₂Ph (R* = Men, ( 4a ); Bor, ( 4b )) which reacted with n‐Bu₃SnCl forming the requisite tri(n‐butyl)tin compounds n‐Bu₃SnCH(CH₂CH₂OR*)SO₂Ph (R* = Men, ( 5a ); Bor, ( 5b )) as diastereomeric mixtures. The identities of 5a and 5b were unambiguously proved by ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopic measurements. Solutions of 4a afforded crystals of [{LiCH(CH₂CH₂OMen)SO₂Ph}₄] ( 4a′ ) for which the structure was determined by single‐crystal X‐ray crystallography. Complex 4a′ crystallized in a tetrameric structure without any additional solvent molecules. There were found direct Li–C bonds (Li1–C1/Li2–C20 2.231(9)/2.236(9) Å). The tetrahedral donor set of Li is completed by three oxygen atoms. One oxygen atom comes from the OMen substituent via intramolecular coordination and two oxygen atoms come from SO₂ groups of neighboured LiCH(CH₂CH₂OMen)SO₂Ph moieties. Thus, a heterocubane structure with a Li₄S₄ core is built up.     

A note on the Undirected Rural Postman Problem polytope

This note refers to the article by G. Ghiani and G. Laporte ``A branch-and-cut algorithm for the Undirected Rural Postman Problem', Math. Program. 87 (2000). We show that some conditions for the facet-defining property of the basic non-trivial inequalities are not sufficient and that the Rural Postman Problem polytope is more complex even when focusing on canonical inequalities only.     

Contamination caused by ion-exchange resin!? Consequences for ultra-trace analysis

Well known sources of contamination are the laboratory environment, vessels, reagents and handling of the sample. Attention is drawn to the importance of cationic impurities included in the ion-exchangers used for trace-matrix separations (TMS) at the sub-ng/g-level. The usual rinsing and conditioning of the resins does not remove all adhering metals and thus leads to contaminated eluates in analytical work. High and badly reproducible blanks are observed, in particular for Na, Mg, Al, K, Cr, Fe, Zn and Ba. They are introduced during the polymerization process and are not ionically bound but obviously included in the polymer matrix. Any time when another “nest” of inclusion is opened in the resin column by mechanical stress, the next irreproducible event of contamination occurs.     

The complexity of computing the tutte polynomial on transversal matroids

The complexity of computing the Tutte polynomialT(M,x,y) is determined for transversal matroidM and algebraic numbersx andy. It is shown that for fixedx andy the problem of computingT(M,x,y) forM a transversal matroid is #P-complete unless the numbersx andy satisfy (x−1)(y−1)=1, in which case it is polynomial-time computable. In particular, the problem of counting bases in a transversal matroid, and of counting various types of “matchable” sets of nodes in a bipartite graph, is #P-complete.     

Principles and applications of quality control by near infrared spectroscopy using the example of polymer additives

Due to its easy application, modern Near Infrared instrumentation is paid increasing attention when considering quality control in the chemical plant. The philosophy of spectrometric quality control and its possibilities and limitations are discussed on the basis of information theory considerations. Considering a group of 74 polymer additives it is shown how, by differentiated calibration with the aid of principal component analysis (PCA), a system could be designed for successfully controlling the quality of incoming products.     

Banking behaviour after the lifecycle event of “moving in together”: An exploratory study of the role of marketing investments

This study addresses an important issue for both managers and researchers: whether it is advantageous for financial services providers to invest in youth marketing. More specifically, the effectiveness of these investments is evaluated in terms of retention proneness once youngsters enter the lifecycle event of “moving in together”. The study identifies eight constructs of youth marketing and contrasts their impact against the best deal when youngsters decide to move in together and consequently experience the need to buy their first collectivized financial products, such as a joint account or a mortgage for their new home. Furthermore, the influence of the partner, prior patronage behaviour, customer demographics and psychographic variables are tested for. The findings of the study reveal that: (i) individuals are likely to change their banking behaviour during crucial lifetime events such as moving in together, (ii) not all youth marketing investments are equally effective, while (iii) the best deal components (e.g. convenience, price conditions, etc.) have a major impact.