Alkyl groups oxidation

Alkylfluotenes, preparation, 16 Alkyl groups, oxidation to carboxyl groups, 421... 

Aromatic side chain alkyl group oxidation—e.g., toluene oxidation to benzoic acid and... 

SeeSecondary alcohols can be prqiared in satisfactory yield by reaction of (he anion of this reagent with trialkylboianes in the presence of excess mercuric chloride to induce migration of two alkyl groups. Oxidation (alkaline HzOg) of the intermediate borane compound leads to the alcohol. ... 

If you want to get the other regioisomer, with the heteroatom at the end, you can use hydro-boration (Chapter 19) or the radical reactions described in the next section. Here is a brief reminder of hydroboration. Reaction between a borane having at least one B-H bond with an alkene gives an alkyl borane in which all the hydrogens are replaced by alkyl groups. Oxidation gives the terminal alcohol. 

The general reaction path operative in metal ion (complex) catalyzed alkane (alkyl group) oxidation consists in the generation of free radicals, which subsequently react with dioxygen to produce hydroperoxy radicals and, via H-atom abstraction, hydroperoxides. The latter are often stable products but also important intermediates in further oxidation. Hydroperoxides can decompose thermally to an alcohol and 0 ... 

The structures of typical ligands were shown earlier in Figure 1.9 and will also be shown later in Figures 3.1 and 3.2. Complexes include some metal halides, hydrates, amines, amides and imides, such as Ti(NR2)4 (R is an alkyl group), oxides, H3B NR3 (a borane-amine adduct), Co(MNT)2 (MNT = maleonitrile dithiolate), Cupc (pc = phthalocyanine), Mo(CO)6, cluster carbonyls, and metal acetylacetonate derivatives. 

The introduction of additional alkyl groups mostly involves the formation of a bond between a carbanion and a carbon attached to a suitable leaving group. S,.,2-reactions prevail, although radical mechanisms are also possible, especially if organometallic compounds are involved. Since many carbanions and radicals are easily oxidized by oxygen, working under inert gas is advised, until it has been shown for each specific reaction that air has no harmful effect on yields. 

Alkyl groups attached to aromatic rings are oxidized more readily than the ring in alkaline media. Complete oxidation to benzoic acids usually occurs with nonspecific oxidants such as KMnO, but activated tertiary carbon atoms can be oxidized to the corresponding alcohols (R. Stewart, 1965 D. Arndt, 1975). With mercury(ll) acetate, allyiic and benzylic oxidations are aJso possible. It is most widely used in the mild dehydrogenation of tertiary amines to give, enamines or heteroarenes (M. Shamma, 1970 H. Arzoumanian. 1971 A. Friedrich, 1975). 

Out first example is 2-hydroxy-2-methyl-3-octanone. 3-Octanone can be purchased, but it would be difficult to differentiate the two activated methylene groups in alkylation and oxidation reactions. Usual syntheses of acyloins are based upon addition of terminal alkynes to ketones (disconnection 1 see p. 52). For syntheses of unsymmetrical 1,2-difunctional compounds it is often advisable to look also for reactive starting materials, which do already contain the right substitution pattern. In the present case it turns out that 3-hydroxy-3-methyl-2-butanone is an inexpensive commercial product. This molecule dictates disconnection 3. Another practical synthesis starts with acetone cyanohydrin and pentylmagnesium bromide (disconnection 2). Many 1,2-difunctional compounds are accessible via oxidation of C—C multiple bonds. In this case the target molecule may be obtained by simple permanganate oxidation of 2-methyl-2-octene, which may be synthesized by Wittig reaction (disconnection 1). 

Derivatives in which the substituents are already in a higher oxidation state than alkyl groups can be good precursors of acids. Acids can be prepared by the oxidation of alcohols. 

When two alkyl groups are present on the ring both are oxidized... 

Oxidation (Section 11 13) Oxidation of alkylben zenes occurs at the benzylic position of the alkyl group and gives a benzoic acid derivative Oxidiz mg agents include sodium or potassium dichro mate in aqueous sulfuric acid Potassium perman ganate (KMn04) is also an effective oxidant... 

Alkylated aromatics have excellent low temperature fluidity and low pour points. The viscosity indexes are lower than most mineral oils. These materials are less volatile than comparably viscous mineral oils, and more stable to high temperatures, hydrolysis, and nuclear radiation. Oxidation stabihty depends strongly on the stmcture of the alkyl groups (10). However it is difficult to incorporate inhibitors and the lubrication properties of specific stmctures maybe poor. The alkylated aromatics also are compatible with mineral oils and systems designed for mineral oils (see Benzene Toulene Xylenes and ethylbenzene). ... 

Moderate yields of acids and ketones can be obtained by paHadium-cataly2ed carbonylation of boronic acids and by carbonylation cross-coupling reactions (272,320,321). In an alternative procedure for the carbonylation reaction, potassium trialkylborohydride ia the presence of a catalytic amount of the free borane is utilized (322). FiaaHy, various tertiary alcohols including hindered and polycycHc stmctures become readily available by oxidation of the organoborane iatermediate produced after migration of three alkyl groups (312,313,323). 

An additional curious feature of alkylaromatic oxidation is that, under conditions where the initial attack involves electron transfer, the relative rate of attack on different alkyl groups attached to the same aromatic ring is quite different from that observed in alkane oxidation. For example, the oxidation of -cymene can lead to high yields of -isopropylbenzoic acid (2,205,297,298). 

Neoprene—phenohc contact adhesives, known for thein high green strength and peel values, contain a resole-type resin prepared from 4-/-butylphenol. The alkyl group increases compatibiHty and reduces cross-linking. This resin reacts or complexes with the metal oxide, eg, MgO, contained in the formulation, and increases the cohesive strength of the adhesive. In fact, the reactivity with MgO is frequently measured to determine the effectiveness of heat-reactive phenoHcs in the formulation. 

Alkoxides of nonmetals are described in articles about the corresponding compounds (see Boron COMPOUNDS, Boron oxides Silicon compounds). Metal alkyls, in which the alkyl group is bound direcdy to the metal, are also discussed elsewhere (see Aluminum compounds). 

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