Structure of solid monolayers and multilayers of n -hexane on graphite

We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules are observed to attain the perpendicular orientation at monolayer coverage. Dedicated to Professor C N R Rao on his 70th birthday     

Vibrational spectra of (NH4)3ZnCl5

IR and Raman spectra of (NH₄)₃ZnCl₅ have been recorded. The observed spectra have been analysed on the basis of the vibrations of ZnCl ₄ ²⁻ and NH ₄ ⁺ ions. The appearance of multiple Raman bands indicates the presence of two different types of ammonium ions. The effect of anisotropic crystalline field over the ZnCl₄ and NH₄ tetrahedra is also discussed. The assignment of internal modes has been verified by the potential energy distribution calculations.     

Reduced cycle indices and their applications in enumeration of NMR signals and equivalence classes

An efficient technique is formulated based on a polynomial structure which we call the reduced cycle index for the enumeration of equivalence classes and NMR signals under group action. The reduced cycle indices are shown to be the cycle index polynomials of a subset of significantly smaller order of the point group of the molecule. Thus, the reduced cycle indices are much simpler and their use leads to a considerable reduction in tile computation of the generating functions from the cycle indices and irreducible representations contained in a set.Alfred P. Sloan Fellow; Camille and Henry Dreyfus Teacher-Scholar.     

Symmetry operators of generalized wreath products and their applications to chemical physics

Symmetry operators of generalized wreath product groups are formulated. Several applications of these operators to nonrigid molecular problems in chemical physics are outlined.     

Site-specific cleavage of human telomerase RNA using PNA-neocuproine.Zn(II) derivatives

Here we report the synthesis of a novel PNA based neocuproine.Zn RNA cleaving agent; we demonstrate that such agents sequence specifically cleave a synthetic RNA target and in particular the RNA component of human telomerase.     

On the claisen rearrangement of 1,4-diaryloxy-2-butynes

A proton nmr follow-up provided conclusive evidence for the involvement of two sequential Claisen rearrangements in the thermal rearrangement of 1,4-diaryloxy-2-butynes $\text{1}$to 11a-methylpterocarpans $\text{3}$. A detailed study of the rearrangement of 1,4-diaryloxy-2-butynes $\text{1}$ in polyethyleneglycol-200 (PEG-200), indicated a definite possibility of selective synthesis of either benzofuron (3,2-b )benzofuran $\text{4}$ or benzofuro(2,3-b)benzofuran $\text{5}$ by varying the temperature of the reaction alone     

Spectrophotometric determination of the stability constants of HgCl(-)3 and HgCl(2-)4 in aqueous ethanol

The stability constants of HgCl(-)(3) and HgCl(2-)(4) in 60% aqueous ethanol (v/v) were determined by spectroscopy at 25 degrees and constant ionic strength and acidity; beta(1) was 3 +/- 1 and beta(2) 9 +/-3.     

On the maximal length of two sequences of integers in arithmetic progressions with the same prime divisors

In this paper we consider an analogue of the problem of Erds and Woods for arithmetic progressions. A positive answer follows from theabc conjecture. Partial results are obtained unconditionally.