Alcohols dimeric, tert

Would you expect the OH stretching frequencies in 2,3-dimethyl-2,3-butanediol to be shifted from the value in tert-butyl alcohol, even in dilute solution. Identify the OH stretching frequencies in the diol and compare them to tert-butyl alcohol. Rationalize your observations by comparing the geometry of the diol with those of tert-butyl alcohol and tert-butyl alcohol dimer. 

Class (3) reactions include proton-transfer reactions of solvent holes in cyclohexane and methylcyclohexane [71,74,75]. The corresponding rate constants are 10-30% of the fastest class (1) reactions. Class (4) reactions include proton-transfer reactions in trans-decalin and cis-trans decalin mixtures [77]. Proton transfer from the decalin hole to aliphatic alcohol results in the formation of a C-centered decalyl radical. The proton affinity of this radical is comparable to that of a single alcohol molecule. However, it is less than the proton affinity of an alcohol dimer. Consequently, a complex of the radical cation and alcohol monomer is relatively stable toward proton transfer when such a complex encounters a second alcohol molecule, the radical cation rapidly deprotonates. Metastable complexes with natural lifetimes between 24 nsec (2-propanol) and 90 nsec (tert-butanol) were observed in liquid cis- and tra 5-decalins at 25°C [77]. The rate of the complexation is one-half of that for class (1) reactions the overall decay rate is limited by slow proton transfer in the 1 1 complex. The rate constant of unimolecular decay is (5-10) x 10 sec for primary alcohols, bimolecular decay via proton transfer to the alcohol dimer prevails. Only for secondary and ternary alcohols is the equilibrium reached sufficiently slowly that it can be observed at 25 °C on a time scale of > 10 nsec. There is a striking similarity between the formation of alcohol complexes with the solvent holes (in decalins) and solvent anions (in sc CO2). 

Both the ally lie alcohol and tert-hutyX hydroperoxide are achiral, but the product epoxide is formed in high optical purity. This is possible because the catalyst, titanium tetraiso-propoxide, forms a chiral (possibly dimeric [36]) complex with resolved diethyl tartrate [(+)-DET] which binds the two achiral reagents together in the reactive complex. The two enantiotopic faces of the allylic double bond become diastereotopic in the chiral complex and react at different rates with the tert-butyl hydroperoxide. Many other examples may be found in recent reviews [31, 37-39]. 

Use SpartanView to measure the 0-H bond distance and identify the 0-H stretching vibration of (ert-hutyl alcohol. Next, measure the O—H bond distances and identify the two stretching vibrations in tert-butyl alcohol dimer. How does dimerization affect the hydrogen-bonded -OH group, and how does it affect the other -OH group ... 

Magnesium/hydrogen chloride Dimeric tert. alcohols from ketones... 

Typical isobutylene, as suppHed to the butyl mbber process, has a purity in the range of 95—99%, and includes varying amounts of propene, 1-butene, 2-butene, isobutylene dimer, and tert-huty alcohol, and trace quantities of a variety of oxygen-containing compounds, depending on the process employed. 

The heterogeneous catalytic system iron phthalocyanine (7) immobilized on silica and tert-butyl hydroperoxide, TBHP, has been proposed for allylic oxidation reactions (10). This catalytic system has shown good activity in the oxidation of 2,3,6-trimethylphenol for the production of 1,4-trimethylbenzoquinone (yield > 80%), a vitamin E precursor (11), and in the oxidation of alkynes and propargylic alcohols to a,p-acetylenic ketones (yields > 60%) (12). A 43% yield of 2-cyclohexen-l-one was obtained (10) over the p-oxo dimeric form of iron tetrasulfophthalocyanine (7a) immobilized on silica using TBHP as oxidant and CH3CN as solvent however, the catalyst deactivated under reaction conditions. 

Butane, 1,4-diiodo-, 30, 33 2-Butanone, 3-acetamido-, 33,1 n-BuTYLACETYLENE, 30, IS tert-Butyl alcohol, 30, 19, 20 32, 20 ierl-Butylbenzene, 32, 91 n-Butyl bromide, 30, 16 tert-Butyl hypochlorite, 32, 20 n-Butyl iodide, 30, 34 Butylketene dimer, 31, 71 -ter -Butylphenyl salicylate, 32, 26 Butyrchloral, 33, IS Butyric acid, a, y-dicyano-o-phenyl-, ethyl ester, 30, 80... 

Hydrodimerization of olefinsIn addition to dehydrodimerization of alkanes 15. 198), hydrodimerization of alkenes can be effected by mercury-photosensitiza- jon, and has the advantage that it is applicable to a wide range of unsaturated wbstrates alcohols and derivatives, ketones, and others. Since the hydrogen adds to ae alkene to give the most stable intermediate (tert > sec > primary), this dimeriza-son can be regioselective. The last example shows that cross-dimerization is possible In this case the hydrodimer of both components is also formed, but in lower ld. 

Chiral epoxides are important intermediates in organic synthesis. A benchmark classic in the area of asymmetric catalytic oxidation is the Sharpless epoxidation of allylic alcohols in which a complex of titanium and tartrate salt is the active catalyst [273]. Its success is due to its ease of execution and the ready availability of reagents. A wide variety of primary allylic alcohols are epoxidized in >90% optical yield and 70-90% chemical yield using tert-butyl hydroperoxide as the oxygen donor and titanium-isopropoxide-diethyltartrate (DET) as the catalyst (Fig. 4.97). In order for this reaction to be catalytic, the exclusion of water is absolutely essential. This is achieved by adding 3 A or 4 A molecular sieves. The catalytic cycle is identical to that for titanium epoxidations discussed above (see Fig. 4.20) and the actual catalytic species is believed to be a 2 2 titanium(IV) tartrate dimer (see Fig. 4.98). The key step is the preferential transfer of oxygen from a coordinated alkylperoxo moiety to one enantioface of a coordinated allylic alcohol. For further information the reader is referred to the many reviews that have been written on this reaction [274, 275]. 

This dimer reacts as two molecules of free 5- alkyli-soxazolyl-3-isocyanate with secondary amines or with alcohols to give the corresponding ureas or carbamates useful as agrochemicals or fine chemicals intermediates. For example, 3-amino-5-tert-butyl isoxazole is a key intermediate for 3- 5-tert-butylisoxazolyl)-1,1-dimethyl urea (common name Isouron) which is useful as a herbicide for sugar cane and other crops (Ref. 180) [Scheme 127]. 

The well-known Sharpless system for the enantioselective epoxidation of allyl alcohols has been investigated [23]. This system employs a tetra-alkoxy titanium precursor, a dialkyltartrate as an auxiliary, and an alkyl hydroperoxide as oxidant, to effect the enantioselective epoxidation. The key intermediate is thought to be a dimeric complex in which titanium is simultaneously coordinated to the chelating tartarate ligand, the substrate in the form of an oxygen bound / -allyl-oxide and an -tert-butylperoxide. 

Selectivity to ETBE is usually very high and the main side reactions are isobutene dimerization with formation of 2,4,4-trimethyl-l-pentene and 2,4,4-trimethyl-2-pentene (DIB), ethanol self-condensation to diethyl ether (DEE), water addition to isobutene with formation of tert-butyl alcohol (TBA) and the etherification of linear butenes, if present, to produce ethyl sec-butyl ether (ESBE). 

The absorption of isobutene in subazeotropic aqueous ethanol, to give ETBE and tert-butyl alcohol (TBA) was investigated [58]. The experiments were conducted in a stainless steel autoclave of one liter capacity. The catalyst used was Amberlyst-15, which is an acidic, macroporous cation exchange resin, in the form of spherical beads. In the ETBE synthesis reaction using ethanol and isobutene, the side reactions are the dimerization of isobutene to form diisobutene and the formation of diethyl ether. These byproducts show a tendency to increase with an increase in reaction temperature. Hence, the... 

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