Hydroxyl groups bonds

Asymmetric epoxidation is another important area of activity, initially pioneered by Sharpless, using catalysts based on titanium tetraisoprop-oxide and either (+) or (—) dialkyl tartrate. The enantiomer formed depends on the tartrate used. Whilst this process has been widely used for the synthesis of complex carbohydrates it is limited to allylic alcohols, the hydroxyl group bonding the substrate to the catalyst. Jacobson catalysts (Formula 4.3) based on manganese complexes with chiral Shiff bases have been shown to be efficient in epoxidation of a wide range of alkenes. 

In the formation of bromohydrin, bromine bonds at the least substituted carbon (from nucleophilic attack by water), and the hydroxyl group bonds at the more substituted carbon (i.e., the carbon that accommodated more of the positive charge in the bromonium ion). 

Summarizing, it can be said that the existence of surface hydroxyl groups on silica-alumina is beyond doubt. However, in chemical reactions all of the hydroxyl groups behave just like silanol groups on silica. No conclusive evidence for the existence of hydroxyl groups bonded to aluminum ions was ever obtained. The most that can be said is that surface silanol groups are much more stable than A1—OH groups. 

Alcohol An organic molecule that contains a hydroxyl group bonded to a saturated carbon. 

The hydroxyl group bonded to a chiral carbon atom in compound 134 represents a possible site for the formation of a stable enzyme-inhibitor complex with adenosine deaminase (ADA), as in 5-9-(2 -hydroxypropyl) adenine and its T-alkyl derivatives. Moreover, the influence of the nitrogen atom on C-3 regarding the inhibitory activity against ADA deserves further investigation. The substituent on C-2 of the nucleus constitutes the third structural element, whose influence on the biological activity of the molecule must also be considered (89JHC39). 

An alcohol with the hydroxyl group bonded to a carbon atom of a carbon-carbon double bond. Most enols are unstable, spontaneously isomerizing to their carbonyl tautomers, called the keto form of the compound. See tautomers, (p. 411)... 

Compounds with a hydroxyl group bonded directly to an aromatic (benzene) ring are called phenols. Phenols have many properties similar to those of alcohols, while other properties derive from their aromatic character. In this chapter, we consider the properties of phenols that are similar to those of alcohols and note some of the differences. In Chapter 16, we consider the aromatic nature of phenols and the reactions that result from their aromaticity. 

Classification of alcohols. Alcohols are classified according to the type of carbon atom (primary, secondary, or tertiary) bonded to the hydroxyl group. Phenols have a hydroxyl group bonded to a carbon atom in a benzene ring. 

A compound with a hydroxyl group bonded directly to an aromatic ring. (p. 426)... 

An intermediate in the formation of an imine, having an amine and a hydroxyl group bonded to the same carbon atom. (p. 851)... 

The cluster approach opens the way for a direct quantum-chemical calculation of the influence of the nearest environment on OH vibration frequencies (12). In such a computation, the scheme of the neutral ionic cluster (12,144) is used that allows one to construct easily a consistent set of the required cluster structures. Two examples are clusters 7a and 7b. Cluster 7a models the hydroxyl group bonded with the A1 atom in tetrahedral coordination. Cluster 7b simulates the bridged hydroxyl group linking two... 

The hydroxyl group bonded to the chiral carbon farthest from the carbonyl group points to the right in a D sugar, and points to the left in an L sugar. 

Enols are organic compounds that have a hydroxyl group bonded to a carbon atom that is attached to another carbon atom by a double bond. Change in bond energies shows that the event is exothermic so potential energy of keto tautomer is lower than that of enol tautomer. It means that keto tautomer is more stable. 

In the synthesis of a deoxyribonucleotide, the hydroxyl group bonded to C-2 of the ribose ring is replaced by H, with... 

Spectroscopic evidence for mechanism (2), arsenic adsorption on oxoanion precipitates, has been provided by Myneni (1995) and Myneni et al. (1997) in the arsenate-ettringite system. Arsenate was found to adsorb to different sites as a function of sorption density. At low sorption density, As oxoanions exchange for surface hydroxyl groups bonded to Al atoms and at higher sorption densities As oxoanions exchange for surface hydroxyl groups bonded to Ca atoms, with minor bonding to Al atoms (Table 2). 

Thus it is composed of a carbonyl group and a hydroxyl group bonded to a carbon atom. The carbon-oxygen unsaturation within the carboxyl group is of a different order from the carbon-to-carbon unsaturation in the alkyl chain in unsaturated fatty acids. For this reason, fatty acids in which no double bond is present except that in the carboxyl group are called saturated. 

Kirutenko, Zhdanov, Bobrov et al. [43,45,46] proved the presence of hydroxyl groups bonded not only with three-coordinated but also with tetra-coordinated boron atoms. 

A hydroxyl group bonded directly to either ring in the 3- or 4- position. 

R = Ph), which shows evidence of 6-carbonyl and 5-hydroxyl groups bonded to an almost planar heterocyclic ring <9lH(32)ll8l>. 

A dideoxynucleotide is one that has hydrogen atoms rather than hydroxyl groups bonded to both the 2 and 3 carbons of the five-carbon sugar. 

Figure 6 shows in addition the characteristic bands of pure silica, that is, 950 (Si-O-Si, axial deformation), 810 (Si-O-Si, axial deformation), and 600 cm (Si-O-Si, angular deformation) [23, 24], The characteristic peaks for the hydroxyl group bonds can also be observed in the range of 3,400 cm [23],... 

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