Methylene groups s. a. Hydrocarbons

The diameters of simple aliphatic hydrocarbon chains match well with the size of a-cyclodextrin s (a-CD) hydrophobic cavity, which in aqueous solution contains in its interior several water molecules (Fig. 3). Sequential insertion of methylene groups of the hydrocarbon chain into the a-CD cavity is accompanied by expulsion of water molecules into the bulk solvent. In addition, several water... 

Benzaldehydes. A soln. of ceric ammonium nitrate in aq. 50%-acetic acid added to p-methoxybenzyl alcohol, warmed a few min. on a steam bath if necessary, and the product isolated when the orange color has turned pale yellow -> p-methoxybenzaldehyde. Y ca. 94%. F. e. s. W. S. Trahanovsky and L. B. Young, Soc. 1965, 5777 aldehydes and acoxy compounds from hydrocarbons s. J. Org. Chem. 31, 2033 (1966) also partial conversion of methyl to aldehyde groups, and keto from methylene groups s. L. Syper, Tetrah. Let. 1966, 4493. 

Two physically reasonable but quite different models have been used to describe the internal motions of lipid molecules observed by neutron scattering. In the first the protons are assumed to undergo diffusion in a sphere [63]. The radius of the sphere is allowed to be different for different protons. Although the results do not seem to be sensitive to the details of the variation in the sphere radii, it is necessary to have a range of sphere volumes, with the largest volume for methylene groups near the ends of the hydrocarbon chains in the middle of the bilayer and the smallest for the methylenes at the tops of the chains, closest to the bilayer surface. This is consistent with the behavior of the carbon-deuterium order parameters,. S cd, measured by deuterium NMR ... 

It might be instructive to consider the impact of molar mass on the physical properties of a regular series of saturated organic hydrocarbons, called a homologous series. Let s start with the simplest member, methane, CH4, and, on papery sequentially add one CH2 unit (or methylene group) to build the series. To start, consider writing methane as CH3-H, and then insert CH2 into the bond between the CH3 and the H. The result is ethane, CH3-CH2-... 

The IV is defined as an average total number of double bonds per mole in a mixture of fatty materials. It is not a good descriptor for correlating physical and chemical properties with fatty acid composition in biodiesel. For example, the IV does not provide any information on structural factors such as number of allylic or bis-allylic methylene groups or location of double bond(s) within the hydrocarbon chain. Knothe (2002) recommended alternative indices termed allylic position equivalents (APE) and Ws-allylic position equivalent (BAPE) based on the total number of allylic and bis-allylic positions present in the fatty acid chains. 

Potassium hydroxide or alkoxide is not always necessary the hydrazones of Michler s ketone, fluorenone, and benzophenone yield the corresponding hydrocarbons in the presence of hydrazine hydrate alone,508 and so do the hydrazones of some ketones that contain a sulfo group, e.g., 4-(methylsulfonyl)-acetophenone hydrazone.509 Apparently these decompositions occur when the methylene group of the hydrazone contains mobile hydrogen atom. 

In addition to decarboxylation, the oxidation of acids yields hydro-peroxy, hydroxy, keto groups, lactones, and mono- and dicarboxylic acids of lower molecular weight. The mechanism of the oxidation of acids is similar to that for hydrocarbons. The reactivity of mono- [300] and dicarboxylic acids [216] with respect to cumylperoxy radicals was measured by oxidation in the presence of cumyl hydroperoxide as source of R02 (see Table 15). The reactivities of methylenic groups in mono- and dicarboxylic acids and in rc-paraffin acids are close. For example, at 100° C, feCH2 X 102 (1 mole-1 s-1) = 4.8 (n-decane), 10.0 (glutaric, sebacic, j3,7 groups), 6.4 (a-CH2 of dibasic acids), 8.0 (for monocarboxylic acids), and 11.0 (>CH2 for propionic acid). 

Solid 2-isopropyl-1,3-benzodithiole 1,1,3,3-tetroxide added to a suspension of NaH in THF, treated with 2-phenylethyl bromide when H2 evolution had ceased, and heated at 80° for 24h - intermediate (Y 75%), in methanol at 50° treated in 3 portions over 3 h with Mg-turnings, and worked up after ca. 4 h - 4-methylpentyl-benzene (Y 72%). This is part of a multistep synthesis of hydrocarbons from two halide molecules with insertion of a methylene group. F.e., also 1,1-disulfonylcyclo-pentanes from 1,4-diiodides, s. E.P. Kundig, A.F. Cunningham, Jr., Tetrahedron 44, 6855-60 (1988). 

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