Methine group hydrocarbons

By comparing a number of aliphatic hydrocarbons of different structure, Mare and RoCek ° compute relative rates of oxidation of methyl, methylene and methine groups to be 1 114 7000-18,000. 

Since hydrocarbon subunits (methyl, methylene and methine groups) are not polarized to a great extent, their nature can be defined by a polar substituent. The high acidity of the a-hydrogen atoms of carbonyl compounds, nitriles, sulfones, and nitroalkanes follows from polarity alternation, the carbon atoms being a donor next to the acceptor substituent. 

Two systems (246,247) will be discussed in this subsection. The nomenclature of these compounds, as of other borazaromatics, has been a point of controversy. Whereas the authors in this field generally followed the procedure of naming these compounds after the isoconjugate parent aromatic hydrocarbon with prefixes like bora and aza indicating the replacement of a methine group by these atoms, in Chemical Abstracts the principal names are derived by reference to the azaborine system. In this Section and in Section... 

Potassium permanganate impregnated on alumina oxidizes arenes and alkylarenes to ketones under microwave activation [69c]. Potassium perman-ganate-triethylamine is a convenient reagent for the oxidation of benzylic methyl, methylene and methine groups [70a], Aqueous solutions of permanganate oxidize methane at 40-100 °C to produce carbon dioxide as the sole product [70b], Oxidation of hydrocarbons containing weak C-H bonds (9,10-dihydro-... 

The replacement of a methylene or methine group with sulfur are often named by using the term "thia" in conjunction with the name of the corresponding hydrocarbon. 

Oxidations with chromic oxide encompass hydroxylation of methylene [544] and methine [544, 545, 546] groups conversion of methyl groups into formyl groups [539, 547, 548, 549] or carboxylic groups [550, 55i] and of methylene groups into carbonyls [275, 552, 553, 554, 555] oxidation of aromatic hydrocarbons [556, 557, 555] and phenols [559] to quinones, of primary halides to aldehydes [540], and of secondary halides to ketones [560, 561] epoxidation of alkenes [562, 563,564, and oxidation of alkenes to ketones [565, 566] and to carboxylic acids [567, 565, 569]. 

In alkanes (aliphatic or saturated hydrocarbons) aU of the CH hydrogen absortions are typically found from about 0.7 to 1.7 ppm. Hydrogens in methyl groups are the most highly shielded type of proton and are found at chemical shift values lower (0.7-1.3 ppm) then methylene (1.2-1.2 ppm) or methine hydrogens (1.4-1.7 ppm). 

The second overtone region (1150-1210 nm or 8264-8696 cm ) has also been used for quantitative measurements, in particular to measure methyl, methylene, methine, and aromatic contributions. The methyl groups of long-chain paraffinic hydrocarbons appear between 8365 and 8375 cm (1194-1195nm). In pentane and hexane, the methyl group absorbs at 8396 cm (1191 nm), in heptane it absorbs at 8388 cm (1192 nm), and in decane it is at 8378 cm (1194 nm). See Figure 2.4. 

The bending modes associated with the methine hydrogen are hard to identify in most hydrocarbons. (The in-plane bend of an isolated sp C—H group can be particularly important, however, in certain heteroatom systems see discussion of the aldehyde functional group.)... 

Multivalent substituent groups of acyclic hydrocarbons are designated by attaching the suffixes. ..idene and. ..idyne to the name of the corresponding monovalent group insofar as the free valences are at the same C atom. Multiple occurrence of such structural elements is taken into account with suitable multiplicative infixes. Methylene, =CH2 or -CH2-, is retained as trivial name the group =CH- is sometimes still called methine or methyne. 

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