Alcohols, primary tertiary

Alcohols and alkyl halides are classified as primary secondary or tertiary according to the degree of substitution of the carbon that bears the functional group (Section 2 13) Thus primary alcohols and primary alkyl halides are compounds of the type RCH2G (where G is the functional group) secondary alcohols and secondary alkyl halides are compounds of the type R2CHG and tertiary alcohols and tertiary alkyl halides are com pounds of the type R3CG... 

Dehydration of alcohols (Sections 5 9-5 13) Dehydra tion requires an acid catalyst the order of reactivity of alcohols IS tertiary > secondary > primary Elimi nation is regioselective and proceeds in the direction that produces the most highly substituted double bond When stereoisomeric alkenes are possible the more stable one is formed in greater amounts An El (elimination unimolecular) mechanism via a carbo cation intermediate is followed with secondary and tertiary alcohols Primary alcohols react by an E2 (elimination bimolecular) mechanism Sometimes elimination is accompanied by rearrangement... 

Unbranched primary alcohols and tertiary alcohols tend to react with hydrogen halides without rearrangement The alkyloxonmm ions from primary alcohols react rap idly with bromide ion for example m an Sn2 process Tertiary alcohols give tertiary alkyl halides because tertiary carbocations are stable and show little tendency to rearrange... 

Nitroparaffins are classed as primary, RCH2NO2, secondary, R2CHNO2, and tertiary, R2CNO2, by the same convention used for alcohols. Primary and secondary nitroparaffins exist ia tautomeric equiUbtium with the enoHc or aci forms. 

Perhaps the most valuable reaction of alcohols is their oxidation to yield car-bony compounds—the opposite of the reduction of carbonyl compounds to yield alcohols. Primary alcohols yield aldehydes or carboxylic acids, secondary alcohols yield ketones, but tertiary alcohols don t normally react with most oxidizing agents. 

Because steric factors strongly influence the rate of silylations, primary alcohols are normally silylated much more rapidly than secondary alcohols whereas tertiary alcohols are silylated much more slowly. The same is true for phenols - ortho-substituted phenols such as o-cresol are silylated much more slowly than unsubstituted phenols. Obviously, the same applies to cleavage of silylated alcohols or phenols on transsilylation, e.g. with excess boiling methanol (Section 2.3). 

The optimized reaction conditions were successfully applied to alkoxides derived from primary as well as secondary alcohols. With tertiary alkoxides, the regiose-lectivihes and yields were excellent but the enantioselechvities were comparatively low. Applicahons of the method are presented in Sechons 9.5.5 and 9.6. 

Many transition-metal complexes have been reported as catalysts of this reaction, including [lr(g-Cl)(coe)2]2 [74] and [lrH2(solv.)(PPh3)][SbF6] [75]. The latter catalyst appeared to be a very active and highly selective. The hydroxyl group can be selectively silylated, even in the presence of other potentially reactive C=C and C=0 groups. The order of relative reactivities of alcohol isomers is secondary alcohol > primary alcohol > tertiary alcohol. 

HCHO — primary alcohol RCHO —secondary alcohol R2CO — tertiary alcohol... 

The oxyfunctionalization of alkanes with H2O2 on TS-1 has only been reported very recently [113-114]. Linear or branched alkanes are oxidized to secondary and/or tertiary alcohols and ketones, the latter ones being formed by consecutive oxidation of the secondary alcohols. Primary alcohols are not detected. At 50°C maximum turn-overs of n-hexane of 35 mol/mol Ti were reported... 

Before the synthesis of the pseudoureas was published, Bernthsen and Klinger [6] reported a pseudothiourea synthesis involving the reaction of thioureas with alkyl halides. This reaction was briefly reviewed by Dains [16] and Stieglitz [49, 50], and it found many commercial applications [51-53]. The preparation of isothiouronium salts by the direct action of thiourea and halogen acids on alcohols (primary, secondary, and tertiary) was reported by Stevens [8] and further developed by Johnson and Sprague [54, 55] (Eq. 25). 

Deoxygenation of esters. Esters can be reduced to hydrocarbons by (QH5)3SiH in the presence of a radical generator, di-f-butyl peroxide, at 140°. Highest yields are obtained with acetates yields based on the alcohol decrease in the order secondary > primary > tertiary. Other silanes are much less effective than triphenylsilane, which is required in excess for high yields. Radical initiators such as AIBN or benzoyl peroxide are not useful.1... 

The steric demand ol the /e/7-butyl group in TBSC1 reduces the reactivity of this silylating reagent to such an extent that not only the base imidazole but also the dipolar aprotie solvent DMF must be added. Moreover, primary alcohols react more rapidly than secondary alcohols, while tertiary alcohols are inert under these conditions.16 It is therefore possible to distinguish between the two free hydroxy functions in diol 25. 

Acetylketene (MeC0CH=C=0)—generated by flash photolysis—showed the following selectivities towards functional groups amines > alcohols (primary > secondary > tertiary) aldehydes ketones.19 The results accord with the ah initio calculations, which suggest planar, pseudo-pericyclic transition states. An imidoylketene, PrN=C(Me)CH=C=0, was also generated and showed similar selectivities. 

Interestingly, this strategy was applied to the more reactive propargyl alkoxides allowing for the simultaneously introduction of the three partners at the start of the reaction. In fact, in this case, no side reactions occurred [95]. This process is remarkably versatile, giving good yields of stereodefined 3-arylidene (and alkenyli-dene) tetrahydrofurans 105 with a variety of propargyl alcohols (primary, secondary, and tertiary) and unsaturated halides (aryl iodides, vinyl bromides, and tri-flates) (Scheme 8.45). 

Reaction kinetics with the various reagents becomes faster as their nucleophilicity is increased. The following order of reactivity can be given primary aliphatic amine > primary aromatic amine > secondary aliphatic amine primary alcohol > secondary alcohol > water > tertiary alcohol phenol > mercaptan. 

Primary alcohols are oxidized to aldehydes, n-butanol being the substrate oxidized at the highest rate. Although secondary alcohols are oxidized to ketones, the rate is less than for primary alcohols, and tertiary alcohols are not readily oxidized. Alcohol dehydrogenase is inhibited by a number of heterocyclic compounds such as pyrazole, imidazole, and their derivatives. 

Dehydration of alcohols.1 This iron salt, as well as CuS04 and NaHS04, when supported on silica gel effects dehydration of alcohols in various solvents at 100-125°. The order of reactivity of alcohols is tertiary > secondary > primary. Silica gel is essential for dehydration other solid supports are not effective, and the rate of dehydration is increased by increasing amounts of Si02 and then becomes constant. 

In general, the acid catalyzed esterification of organic acids can be accomplished easily with primary or secondary alkyl or aryl alcohols, but tertiary alcohols usually give carbonium ions which lead to dehydration. The structure of the acid is also of importance. As a rule, the more hindered the acid is alpha to the carbonyl carbon the more difficult esterification becomes (20A). 

Chromic acid test. This test is able to distinguish primary and secondary alcohols from tertiary alcohols. Using acidified dichromate solution, primary alcohols are oxidized to carboxylic acids secondary alcohols are oxidized to ketones tertiary alcohols are not oxidized. (Note that in those alcohols which are oxidized, the carbon that has the hydroxyl group loses a hydrogen.) In the oxidation, the brown-red color of the chromic acid changes to a blue-green solution. Phenols are oxidized to nondescript brown tarry masses. (Aldehydes are also oxidized under these conditions to carboxylic acids, but ketones remain intact see Experiment 31 for further discussion.)... 

Poor yields of alkyl chlorides from primary and secondary alcohols. Primary and secondary alcohols react with HC1 much more slowly than tertiary alcohols, even with zinc chloride added. Under these conditions, side reactions may prevent good yields of the alkyl halides. 

Pyridine complexes of Rh111 have played a central role in the still poorly understood area of catalyzed substitutions at Rh111 centers. Delepine first noted that the consecutive substitution of [RhCl6]3 by pyridine leads to the neutral, and insoluble, [Rhpy3Cl3], but that if the aqueous solvent includes some alcohol, pyridine substitution continues and rans,-[Rhpy4Cl2]+ is the final product (equation 155).784 Delepine showed that primary alcohols all had comparable effects on the rate of formation of [Rhpy4Cl2]+, and that secondary alcohols were less active than primary alcohols.785 Tertiary alcohols proved to be totally inactive, as are ether, dioxane or acetone. Poulenc had also reported that ethanol catalyzed substitutions at Rhiri centers.793... 

In general reaction of an alcohol with the appropriate anhydride or acid chloride in pyridine at 0-20 JC is sufficient. In the case of tertiary alcohols, acylation is very slow in which case a catalytic amount of 4-dimethylaminopyridine (DMAP) can be added to speed up the reaction by a factor of 10,000. Reaction of polyols with acyl chlorides (1.2 equiv) in the presence of hindered bases (2.0equiv) such as 2,4,6-collidine, diisopropylethylamine or 1,2,2,6,6-penta-methylpiperidine in dichloromethane at -78 °C leads to selective acylation of a primary alcohol. Primary alcohols can also be acylated selectively with isopro-penyl acetate or acetic anhydride in the presence of a catalytic amount of 1,3-dichlorotetrabutyldistannoxane 325.1 [Scheme 4.325].602 The catalyst 325.1 is available commercially or can be easily prepared by simply mixing dibutyltin oxide and dibutyldichlorostannane. No aqueous workup is necessary since the catalyst can be removed by simple chromatography. 

Isomerization of allylic alcohols. These reagents, in a 3 1 ratio, catalyze the rearrangement of primary allylic alcohols to tertiary allylic alcohols. 

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