Structure Studies of Solutions of Large Organic Molecules. II. End-to-End Distances of Alkanes from C8− to C22−

Abstract

En~-to-~nd distances. for a s~ries of alkanes in the range Cs-to C22-have been measured by the technique descrIbed m the precedmg artIcle. There appears to be good agreement with the theoretical values of the characteristic ratio (r2)/nI2 cited by Flory. However, there is evidence that solvent effects are present. These are discussed.

On the microstructure of organic solutions of mono-carboxylic acids: Combined study by infrared spectroscopy, small-angle neutron scattering and molecular dynamics simulations

“…According to Table 2, the dimer lengths do not exceed 75% and 70% of the L trans values in the case of MA (%4 nm) and SA (%5 nm) solutions, respectively. This is in agreement with the results of the previous diffraction experiments [53] on iodinated alkane solutions of C 14 H 28 I 2 and C 18 H 36 I 2 , which gave 1.44 and 1.78 nm for the chain end-to-end distances corresponding to 72% and 71% of the all-trans molecule configuration lengths, respectively. From the comparison of the molecule volume, V, with the volume, V trans , calculated for the all-trans isomer (the V/V trans ratio is given in Table 2) one can see a difference between the two solvents.…”

Dielectric increments of amino acids

“…These results might appear surprising, in view of the evidence that, in inert solvents, straight-chain molecules exist in a variety of conformations, the rigidly extended conformation forming a decreasing proportion of the whole as n Journal of the American Chemical Society / 96:3 j February increases. [26][27][28][29] Although this is an acceptable notion for straight-chain molecules in the gas phase, or in comparatively inert solvents, it is unlikely to be correct for zwitterions in polar solvents such as water. In this case {as has already been pointed out30) the very strong interaction between the charged ends of zwitterions with the dipoles of the solvent water molecules will cause the latter to cluster about the ends of the molecules and to extrude as completely as possible the less strongly attracted hydrocarbon chain.…”