1-Phenylethanol, formation

The selectivity is calculated by dividing the initial rate of 1-phenylethanol formation by the initial rate of product formation for the reduction of the cosubstrate. 

Propylene oxide is a colorless, low hoiling (34.2°C) liquid. Table 1 lists general physical properties Table 2 provides equations for temperature variation on some thermodynamic functions. Vapor—liquid equilibrium data for binary mixtures of propylene oxide and other chemicals of commercial importance ate available. References for binary mixtures include 1,2-propanediol (14), water (7,8,15), 1,2-dichloropropane [78-87-5] (16), 2-propanol [67-63-0] (17), 2-methyl-2-pentene [625-27-4] (18), methyl formate [107-31-3] (19), acetaldehyde [75-07-0] (17), methanol [67-56-1] (20), ptopanal [123-38-6] (16), 1-phenylethanol [60-12-8] (21), and / /f-butanol [75-65-0] (22,23). 

Ethylbenzene Hydroperoxide Process. Figure 4 shows the process flow sheet for production of propylene oxide and styrene via the use of ethylbenzene hydroperoxide (EBHP). Liquid-phase oxidation of ethylbenzene with air or oxygen occurs at 206—275 kPa (30—40 psia) and 140—150°C, and 2—2.5 h are required for a 10—15% conversion to the hydroperoxide. Recycle of an inert gas, such as nitrogen, is used to control reactor temperature. Impurities ia the ethylbenzene, such as water, are controlled to minimize decomposition of the hydroperoxide product and are sometimes added to enhance product formation. Selectivity to by-products include 8—10% acetophenone, 5—7% 1-phenylethanol, and <1% organic acids. EBHP is concentrated to 30—35% by distillation. The overhead ethylbenzene is recycled back to the oxidation reactor (170—172). 

A single isomer of 4-phenylperhydropyrido[2,l-c][l,4]oxazin-l-one 319 was isolated from a reaction mixture of 2-bromocyclohexane and 2-azido-2-phenylethanol. The formation of 319 was deduced from azepino[l,2-i]... 

Control experiments do not provide evidence for oxidation of the secondary alcohol groups in the glycoside or for degradation of the ligand backbone. A similar regioselectivity was also observed in a benzyl alcohol/1-phenylethanol model system that showed no proof for the oxidation of the secondary alcohol by formation of acetophenone (18, 23,26). 

The complex [Rh(COD)L L2]+, where L1 = PPh3 and L2 = pyridine, and a neutral benzoate complex, Rh(COD)(PPh3)(OCOPh), also effect highly selective hydrogenation of 1-alkynes to 1-alkenes as well as reduction of 1-alkenes and ketones to alcohols (139) the one equivalent of base required may be related to monohydride formation [Eq. (25)]. The bisphosphine complexes also catalyze reduction of styrene oxide to 2-phenylethanol and phenylacetaldehyde (140) ... 

Fig. 14 Relative dipole bound anion formation rates in RET collisions between Rydberg Xe(nf) atoms and a supersonic beam of (R)-l-phenylethanol (E/ ) with 2-pyrrolidinmethanols (PRand P5).

In a time course study on the conversion of ( )-l-phenylethanol 13 (X=H), formation of acetophenone was observed to a maximum of around 20% during the conversion of (S)- to (R)- alcohol which occurred over 24 h to give (R)-13 in 96 % yield, 99% e.e. The effect of ring substitution on the efficiency of the dera-cemization was notable. While para substituents (Cl, OMe, Me) gave good results, ortho derivatives could not be deracemized and the biocatalyst showed little activity towards meta substituted compounds. On addition of allyl alcohol, improvements in e.e. were obtained, particularly for the conversion of l-(m-methylphenyl)ethanol (from 21 to 94% e.e.). However these improvements did appear to be at the expense of yield (89% diminished to 55%). The authors sug-... 

Reaction of Ser-OMe with benzimino ethyl ester resulted in the formation of an oxazoline without racemization (Scheme 27) (85T2379). After forming an amide with 2-amino-l-phenylethanol, Af-phthalimido AAs were oxidized with CrOs and dehydrated by POCI3 to give substituted oxazoles (91JHC1241). 

In contrast to hydrogenation over noble metals hydrogenation of acetophenone over different nickel catalysts and over copper chromite results in the formation of 1-phenylethanol without hydrogenolysis [43,45,49,50]. 

Finally, there is one more snggested way of making l-(2-phenyl-2-hydroxyethyl)-2-imino-1,3-thiazolidine (38.1.28), which consists of reacting 2-amino-1-phenylethanol with 2-bromoethylisothiocyanate. This leads to the direct formation of the key l-(2-phenyl-2-hydroxyethyl)-2-imino-l,3-thiazohdine (38.1.28), which is transformed to tetramizole by a subsequent reaction with thionyl chloride, and then with acetic anhydride [37]. 

Bi does not adsorb hydrogen, thus a Bi/Pt coverage can be calculated from the hydrogen chemisorption data. It is seen in Figure 2 that there is an excellent correlation between the Bi-coverage of Pt and the rate of 1-phenylethanol oxidation. It seems that the hydrogen chemisorption ability of Pt or the size of active sites ensembles has to be minimized to avoid deactivation. There are indications in the literature that the suppression of hydrogen sorption on a Pt electrode can eliminate the poison formation (20). 

In certain cases, especially for neutral substrates, the formation of covalent p,n-pairs, instead of salts, may be necessary to achieve optical resolution by crystallization. Suitable derivatives are esters of camphanic acid (1) or chrysanthemic acid (2) with racemic alcohols, or esters of menthol (3) and 1-phenylethanol (5) with racemic acids, or hydrazones of menthylhydrazine (4) with racemic aldehydes and ketones. 

Fig. 23.5 Aqueous-organic two-liquid-phase system for microbial production of flavour compounds. Here the formation of 2-phenylethanol from L-phenylalanine is exemplarily shown [120]. The organic solvent used for in situ extraction has to be carefully selected on the basis of multiple criteria, such as biocompatibility, non-flammability and legislative regulations. For a more detailed description of flavour production in two-phase systems, see Chap. 24 by Larroche et al.

Racemization of (S)-l-phenylethanol in the presence of an Ru p-cymerie binu-clear complex and triethylamine was much faster in [BMIm][BF4] or [BMIm][PF,s] than in toluene [136]. A range of chiral alcohols (Figure 10.17) were resolved in the presence of this complex and immobilized PsL. The reactions were performed in [BM Im][PF6] with the activated ester 2,2,2-trifluoroethyl acetate as the acyl donor (Figure 10.17). A hydrogen donor was required to prevent the formation of partially oxidized byproducts. Enantiomerically pure acetates were isolated in high yield (>85%). 

In the course of irradiation of acetophenone in the presence of 1-phenylethanol, the actual quantum yields for pinacol formation do not exceed 50%, but rise to 71% when PhCH(OD)Me is used for photoreduction of acetophenone in acetonitrile683,684. A conclusion has been reached from this inverse DIE that half the reaction of triplet acetophenone with 1-phenylethanol involves abstraction of an OH hydrogen followed by disproportionation of the initial radical pair back to reactants. A transfer of an O-bonded hydrogen to a triplet ketone is taking place (equation 318) besides the abstraction of hydrogen from... 

Coxon, Steel, and co-workers studied the transformations of a series of phenylalk-anols in fluorosulfuric acid at low temperature to find a variety of reaction modes. Cyclization of 2-phenylethanols, in most of the cases, is accompanied by rearrangement to afford various polycyclic products.319 The formation of propellane 86 was rationalized by the plausible mechanism shown in Eq. (5.123). 

To specify the position and the nature of the transferred hydride, the reaction was performed with 2-propanol-dj as solvent/donor, sodium 2-propylate as base and Fe3(CO)12/PPh3/TerPy as catalyst under optimized conditions. In the transfer hydrogenation of acetophenone a mixture of two deuterated 1-phenylethanols was obtained (Scheme 4.7, 9a and 9b). The ratio between 9a and 9b (85 15) indicated a specific migration of the hydride, albeit some scrambling was detected. However, the incorporation is in agreement with the monohydride mechanism, implying the formation of metal monohydride species in the catalytic cycle. 

Free amino acids are further catabolized into several volatile flavor compounds. However, the pathways involved are not fully known. A detailed summary of the various studies on the role of the catabolism of amino acids in cheese flavor development was published by Curtin and McSweeney (2004). Two major pathways have been suggested (1) aminotransferase or lyase activity and (2) deamination or decarboxylation. Aminotransferase activity results in the formation of a-ketoacids and glutamic acid. The a-ketoacids are further degraded to flavor compounds such as hydroxy acids, aldehydes, and carboxylic acids. a-Ketoacids from methionine, branched-chain amino acids (leucine, isoleucine, and valine), or aromatic amino acids (phenylalanine, tyrosine, and tryptophan) serve as the precursors to volatile flavor compounds (Yvon and Rijnen, 2001). Volatile sulfur compounds are primarily formed from methionine. Methanethiol, which at low concentrations, contributes to the characteristic flavor of Cheddar cheese, is formed from the catabolism of methionine (Curtin and McSweeney, 2004 Weimer et al., 1999). Furthermore, bacterial lyases also metabolize methionine to a-ketobutyrate, methanethiol, and ammonia (Tanaka et al., 1985). On catabolism by aminotransferase, aromatic amino acids yield volatile flavor compounds such as benzalde-hyde, phenylacetate, phenylethanol, phenyllactate, etc. Deamination reactions also result in a-ketoacids and ammonia, which add to the flavor of... 

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