333-45-9Relevant academic research and scientific papers
A Microscopic Hydrophobicity Parameter
Menger, F. M.,Venkataram, U. V.
, p. 2980 - 2984 (1986)
p-Nitrophenyl laurate at 1x1E-5 M in water forms aggregates within which the ester groups hydrolyze slowly (about 1E3 less than a short-chain monomer).Salts of the general structure RNMe3+X- disrupt or destroy the aggregates; the ester groups are thereby "deshielded", and the observed hydrolysis rate increases.The magnitude of the rate increase at a given salt concentration depends on R: the more hydrophobic the R group, the greater the rate enhancement.This observation provided the basis of a "microscopic" hydrophobicity parameter MH which was evaluated for 25 different Rs (e.g., MH=0.73, 0.97, and 1.33 for R=ethyl, n-butyl, and n-hexyl).MH values were used to assess the role of branching, unsaturation, cyclization, aromaticity, halogenation, etc., in hydrophobic association.The parameters correlate well with Hansch ? values for aliphatic substituents but not for aromatic groups.Since the MH scale is based on the specific binding of one molecule to another, it may be well suited for modeling association among bioactive species.
Shape-Selective Recognition of Quaternary Ammonium Chloride Ion Pairs
Li, Dong-Hao,Smith, Bradley D.
, p. 2808 - 2816 (2019/03/26)
Synthetic receptors that recognize ion pairs are potentially useful for many technical applications, but to date there has been little work on selective recognition of quaternary ammonium (Q+) ion pairs. This study measured the affinity of a tetralactam macrocycle for 11 different Q+·Cl- salts in chloroform solution. In each case, NMR spectroscopy was used to determine the association constant (Ka) and the structure of the associated complex. Ka was found to depend strongly on the molecular shape of Q+ and was enhanced when Q+ could penetrate the macrocycle cavity and engage in attractive noncovalent interactions with the macrocycle's NH residues and aromatic sidewalls. The highest measured Ka of 7.9 × 103 M-1 was obtained when Q+ was a p-CN-substituted benzylic trimethylammonium. This high-affinity Q+·Cl- ion pair was used as a template to enhance the synthetic yield of macrocyclization reactions that produce the tetralactam receptor or structurally related derivatives. In addition, a permanently interlocked rotaxane was prepared by capping the end of a noncovalent complex composed of the tetralactam macrocycle threaded by a reactive benzylic cation. The synthetic method provides access to a new family of rotaxanated ion pairs that can likely act as anion sensors, molecular shuttles, or transport molecules.
Benzylic Ammonium Ylide Mediated Epoxidations
Roiser, Lukas,Robiette, Rapha?l,Waser, Mario
supporting information, p. 1963 - 1968 (2016/08/10)
A high yielding synthesis of stilbene oxides using ammonium ylides has been developed. It turned out that the amine leaving group plays a crucial role as trimethylamine gives higher yields than DABCO or quinuclidine. The amine group also influences the diastereoselectivity, and detailed DFT calculations to understand the key parameters of these reactions have been carried out.
