Vibrational spectra and structure of gaseous and solid dimethylboric anhydride

The Raman spectra of gaseous, liquid and solid dimethylboric anhydride (CH₃)₂BOB(CH₃)₂ have been recorded from 10–3500 cm^?1. The IR spectra from 4000–30 cm^?1 have also been recorded. The spectra of the gaseous phase have been interpreted in terms of C₂ symmetry implying a bent B-O-B skeleton with the B(CH₃)₂ groups twisted and consistent with a rather larger barrier to internal rotation about the B-O bonds. The spectra of the crystalline state, however, suggest that the molecular symmetry is altered upon solidification. Isotopic substitution of the oxygen atom by ¹⁸O confirmed that the B-O-B skeleton is linear in the solid state, and the spectra have been interpreted in terms of D_2h molecular symmetry.     

Solubilization chromatography: Ethers,carboxylic acids,and hydrocarbons

Synthetic mixtures of aliphatic and aromatic ethers, satmated fatty acids, and substituted benzenes and naphthalenes were separated by elution through columns of ion-exchange resins with aqueous solutions of acetic acid as eluent An attempt was made to use a resin of low capacity for the separation of such mixtures, and the results of this attempt are used to help elucidate the theory of solubilization chromatography     

Electron impact ionization mass spectra of lithocholyl amides: Evidence for a C(20) to C(23) rearrangement involving the loss of a C4H9 fragment

Amides of lithocholic acid (3α-hydroxy-5β-cholan-24-oic acid) with 6-aminocaproic acid and 4-aminobutyric acid were prepared and examined by electron impact ionization mass spectrometry. Both these compounds gave an unusual [M ? 57]⁺ fragment. Since the product-ion analysis of [M ? 57]⁺ revealed the presence of fragments corresponding to the intact steroid nucleus in addition to that of the original amino acid (6-aminocaproic acid or 4-aminobutyric acid), we concluded that the integrity of the steroid amide had been retained in this fragment. The absence of this fragment from the product-ion spectrum of [M ? CH₃]⁺ rules out the sequential loss from the molecular ion of 15 + 42 u as the origin of this signal. Mass spectrometry of the 24-¹³C-labelled lithocholylcaproylamide showed the retention of the label in the [M ? 57]⁺ fragment. In contrast, the corresponding compound labelled with deuterium at C(23) showed a significant loss of the label during the formation of this product ion at [M ? 58]⁺. In addition, through a combination of derivatization and tandem mass spectrometry, it was demonstrated that this loss of 57 u represented a rearrangement with the expulsion of a C₄H₉ radical from the side-chain spanning C(20) to C(23) resulting in a truncated steroid-amide fragment. This fragmentation pattern has not been observed in bile acid conjugates with N-α-amino acids.     

High-performance liquid chromatographic analysis of basic drugs on silica columns using non-aqueous ionic eluents. I. Factors influencing retention, peak shape and detector response

The use of silica columns together with non-aqueous ionic eluents provides a stable yet flexible system for the high-performance liquid chromatographic analysis of basic drugs. At constant ionic strength, eluent pH influences retention via ionisation of surface silanols and protonation of basic analytes, pKa values indicating the pH of maximum retention. At constant pH, retention is proportional to the reciprocal of the eluent ionic strength for fully protonated analytes and quaternary ammonium compounds. The addition of water up to 10% (v/v) has little effect on retention if the protonation of the analytes is unaffected. Thus, it is likely that retention is mediated primarily via cation exchange with surface silanols. However, additional factors must play a part with compounds such as morphine which give tailing peaks at acidic or neutral eluent pHs.