Primary alcohols, preparation

A method that allows for alcohol preparation with formation of new carbon-carbon bonds Primary sec ondary and tertiary alcohols can all be prepared... 

Esters of nitro alcohols with primary alcohol groups can be prepared from the nitro alcohol and an organic acid, but nitro alcohols with secondary alcohol groups can be esterified only through the use of an acid chloride or anhydride. The nitrate esters of the nitro alcohols are obtained easily by treatment with nitric acid (qv). The resulting products have explosive properties but are not used commercially. 

Eatty alcohols, prepared from fatty acids or via petrochemical processes, aldol or hydroformylation reactions, or the Ziegler process, react with ammonia or a primary or secondary amine in the presence of a catalyst to form amines (10—12). 

Because tertiary alcohols are so readily converted to chlorides with hydrogen chloride, thionyl chloride is used mainly to prepare primary and secondary alkyl chlorides. Reactions with thionyl chloride are nonrrally carried out in the presence of potassium carbonate or the weak organic base pyridine. 

Identify the target alcohol as primary, secondary, or tertiary. A primary alcohol can be prepared by reduction of an aldehyde, an ester, or a carboxylic acid a secondary alcohol can be prepared by reduction of a ketone and a tertiary alcohol can t be prepared by reduction. 

Fig. 9.8 presents another, more complex type of phosphate prodrugs, namely (phosphoryloxy)methyl carbonates and carbamates (9-26, X = O or NH, resp.) [84], Here, the [(phosphoryloxy)methyl]carbonyl carrier appears quite versatile and of potential interest to prepare prodrugs of alcohols, phenols, and amines. The cascade of reactions leading from prodrug to drug as shown in Fig. 9.8 involves three steps, namely ester hydrolysis, release of formaldehyde, and a final step of carbonate hydrolysis (X = O) or A-decar-boxylation (X = NH). Three model compounds, a secondary alcohol, a primary aliphatic amine, and a primary aromatic amine, were derivatized with the carrier moiety and examined for their rates of breakdown [84], The alcohol, indan-2-ol, yielded a carrier-linked derivative that proved relatively... 

Secondary alcohols are much different chemically than primary alcohols, such as natural alcohols. In addition, commercial secondary alcohols are prepared from both even and odd carbon-numbered n-paraffins and thus contain both even and odd carbon-numbered alcohols. Oxo alcohols are primary alcohols, as are natural alcohols. However, oxo alcohols contain from twenty to sixty percent branched chain alcohols and also contain both even and odd carbon-numbered homologs. Ziegler alcohols are very similar to natural alcohols. They are primary alcohols and are a mixture of only even carbon-numbered homologs. The major differences between Ziegler and natural alcohols are trace impurities present and the range of synthetic products, C -C30, available. 

Dialkylnitriloosmium chromates, rteu4 N=0sR2l(CrO4) (1). Preparation.1 These metal chromates are effective catalysts for oxygenation of primary and secondary alcohols.2 Primary alcohols are oxidized exclusively to aldehydes and no esters are formed from secondary alcohols. Primary alcohols are oxidized more rapidly than secondary ones. 

Other oxidants of hexavalent chromium are chromyl chloride and di-/er/-butyl chromate. Chromyl chloride adsorbed on alumina-silica gel from its solution in dichloromethane oxidizes aliphatic and aromatic alcohols at room temperature within hours in 77-100% yields [675]. Di-tert-butyl chromate, prepared in situ from chromyl chloride in tert-butyl alcohol at -70 °C, gives comparable results under similar conditions [674. Di-tert-butyl chromate, prepared from chromium trioxide and tert-butyl alcohol, oxidizes primary aliphatic and aromatic alcohols to the corresponding aldehydes even at low temperatures (1-2 °C) [677, 678]. 

The compound that is formed by oxidation of an alcohol depends upon the number of hydrogens attached to the carbon bearing the —OH group, that is, upon whether the alcohol is primary, secondary, or tertiary. We have already encountered these products—aldehydes, ketones, and carboxylic acids—and should recognize them from their structures, even though we have not yet discussed much of their chemistry. They are important compounds, and their preparation by the oxidation of alcohols is of great value in organic synthesis (Secs. 16.9 and 16.10). 

The most generally useful method for preparing alkyl halides is to make them from alcohols, which themselves can be obtained from carbonyl compounds, as we ll see in Sections 17.4 and 17.5. Because of the importance of the process, many different methods have been developed to transform alcohols into alkyl halides. The simplest method is to treat the alcohol with HCl, HBr, or HI. For reasons that will be discussed in Section 11.5, the reaction works best with tertiary alcohols, R3COH. Primary and secondary alcohols react much more slowly and at higher temperatures. 

Tertiary carbocations may be conveniently prepared in such media from alkyl halides, alcohols, and alkenes. Secondary cations can be observed at low temperatures, but they rearrange readily to more stable tertiary ions. For such cases, special techniques of mixing the reactants, e.g. cocondensation on a cold surface ( molecular beam technique ), have been developed43. Attempts to prepare primary ions in the same manner have not been successful. Methyl and ethyl fluorides exchange halogen but do not generate observable concentrations of cations. All other simple... 

You may remember that to prepare primary alcohols by this method we should start with formaldehyde, and to prepare secondary alcohols we should start with higher aldehydes. 

Protection of the primary and acylation of the secondary alcohol prepares the way for an Ireland-Claisen rearrangement. The E-enolate is produced and the [3,3] sigmatropic rearrangement transmits the chirality across the alkene to set up two new centres. The mechanism of the Ireland-Claisen rearrangement is described above 94 and occurs suprafacially across the backbone of the molecule through a chair-like transition state. We hope you agree both with the relative stereochemistry of the new centres and the E stereochemistry of the new alkene. 

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