Phenols and aliphatic alcohols

We have developed a simple, iterative synthetic method for the preparation of hydroxypropyl derivatives of phenolic and aliphatic alcohols which allows complete definition and control of the degree of chain extension in the products. This methodology has been applied to the preparation of a series of lignin model compounds having hydroxypropyl chain extension degrees of 1-... 

An example in which rate constants are related to equilibrium constants involves the base-catalyzed hydrolysis ofN-phenyl carbamates (Fig. 13.16). As discussed above, these compounds hydrolyze with the dissociation of the alcohol moiety being the rate-determining step. Hence, by using the pA a s of the leaving groups (phenols and aliphatic alcohols), we find a nice correlation to the rates of these reactions. 

Only a few examples have been reported of the etherification of alcohols with resin-bound diarylmethyl alcohols (Entry 5, Table 3.30 Entry 5, Table 3.31 [564]). Diarylmethyl ethers do not seem to offer advantages over the more readily accessible trityl ethers, which are widely used as linkers for both phenols and aliphatic alcohols. Attachment of alcohols to trityl linkers is usually effected by treating trityl chloride resin or 2-chlorotrityl chloride resin with the alcohol in the presence of a base (phenols pyridine/THF, 50 °C [565] or DIPEA/DCM [566] aliphatic alcohols pyridine, 20-70 °C, 3 h-5 d [567-572] or collidine, Bu4NI, DCM, 20 °C, 65 h [81]). Aliphatic or aromatic alcohols can be attached as ethers to the same type of light-sensitive linker as used for carboxylic acids (Section 3.1.3). 

Phenols and aliphatic alcohols abacavir, APAP, almokalant, carvedilol, chloramphenicol, epirubicin, l -OH-estragole, 5-OH-rofecoxib, lorazepam, menthol, 4-methylumbelliferone, 1-naphthol (low), 4-nitrophenol, octyl-gallate, R-oxazepam, propranolol, temazepam, ZDV... 

Derivatization is also useful to detect volatile metabolites. Liu et al. [282] described a specific, rapid, and sensitive in situ derivatization solid-phase microextraction (SPME) method for determination of volatile trichloroethylene (TCE) metabolites, trichloroacetic acid (TCA), dichloroacetic acid (DCA), and trichloroethanol (TCOH), in rat blood. The metabolites were derivatized to their ethyl esters with acidic ethanol, extracted by SPME and then analyzed by gas chromatography/negative chemical ionization mass spectrometry (GC-NCI-MS). After validation, the method was successfully applied to investigate the toxicokinetic behavior of TCE metabolites following an oral dose of TCE. Some of the common derivatization reagents include acetyl chloride and TV-methyl-iV- ft-b u (y Idi methyl si I y I) tro (1 uoroacctam i nc (MTBSTFA) for phenols and aliphatic alcohols and amines, dansyl chloride and diazomethane for phenols, dansyl chloride for amines, acidic ethanol and diazomethane for carboxylic acids, and hydrazine for aldehydes. 

The most common fluorotags (fluorescent reagents) are dansyl chloride and o-phthalaldehyde (OPA). Chromotags include p-bromophenacyl bromide (PBPB) for derivatization of carboxylic acids (K-salts) with a crown ether catalyst, ninhydrin for primary amines forming complexes that have their adsorption maxima at about 570 nm, and dansyl chloride for primary and secondary amines, including amino acids, thiols, imidazoles, phenols, and aliphatic alcohols. 

The basic types of epoxy stabilizers are glycidyl esters - condensation products of epichlorohydrin with phenols and aliphatic alcohols, epoxided esters of higher aliphatic acids, and alicyclic epoxy esters of aliphatic and aromatic acids and alcohols [246, 247, 251-256]. 

A few years later, Drago, et al. (100) made a giant leap forward by relating the heat of bond formation to a shift in the infrared absorption frequency. A linear relationship for certain types of donors (such as oxygen and nitrogen) between the shift in the frequency of the -OH stretching vibration of phenols and aliphatic alcohols, Avqh, and the enthalpy of bond formation was developed. The equation was written. 

The chemical resistance of PCTFE is good but not as good as that of PTFE. Under certain circumstances substances such as chlorosulphonic acid, molten caustic alkalis and molten alkali metal will adversely affect the material. Alcohols, acids, phenols and aliphatic hydrocarbons have little effect but certain aromatic hydrocarbons, esters, halogenated hydrocarbons and ethers may cause swelling at elevated temperatures. 

The reaction between acid chlorides and aliphatic alcohols or phenolic compounds commonly takes place at low to moderate temperature (—10 to 100°C) in solution or by interfacial or dispersion polymerization techniques. It has been widely applied to polyester synthesis. Reviews and books are available on the polymerization techniques as well as on the chemistry of this reaction.2,207 294... 

An interesting variant involves the use of an allylic alcohol as the alkene component. In this process, re-oxidation of the catalyst is unnecessary since the cyclization occurs with /Uoxygen elimination of the incipient cr-Pd species to effect an SN2 type of ring closure. Both five- and six-membered oxacycles have been prepared in this fashion using enol, hemiacetal, and aliphatic alcohol nucleophiles.439,440 With a chiral allylic alcohol substrate, the initial 7r-complexation may be directed by the hydroxyl group,441 as demonstrated by the diastereoselective cyclization used in the synthesis of (—)-laulimalide (Equation (120)).442 Note that the oxypalladation takes place with syn-selectivity, in analogy with the cyclization of phenol nucleophiles (1vide supra). 

Various aldehydes 184 and alcohols have been shown to be competent in the redox esterification of unsaturated aldehydes in the presence of the achiral mesityl triazo-lium pre-catalyst 186. Both aromatic and aliphatic enals participate in yields up to 99% (Table 13). Tri-substituted enals work well (entry 3), as do enals with additional olefins present in the substrate (entries 4 and 7). The nucleophile scope includes primary and secondary alcohols as well as phenols and allylic alcohols. Intramolecular esterification may also occur with the formation of a bicyclic lactone (entry 8). 

The concept of a group is especially important in organic chemistry. A functional group represents a set of atoms that is closely linked with chemical reactivity and defined classes of substances. For instance, the functional group hydroxyl, -OH, is characteristic of the classes alcohol, phenol and enol. Alcohols are often represented by the general formula R-OH, in which R- represents a hydrocarbon group typical of aliphatic and alicyclic substances. 

K values are equal to 1.0 for apolar and many monopolar compounds. For compounds exhibiting weakly bipolar character (e.g., esters, ketones, nitriles), a modest correction with a Kv of about 1.04 can be made. Significant corrections are necessary for primary amines (Kr = 1.10), phenols (KF = 1.15), and aliphatic alcohols (K = 1.30). For a more comprehensive compilation of Kv values, we refer to the literature (e.g., Grain, 1982a). 

Phenolic compounds are, in general, weak acids. Compared to the hydroxyl group of unsubstituted aliphatic alcohols, however, the phenolic OH-group is more acidic. The reason for this is that the anion formed after abstracting the proton from the hydroxyl group is relatively stable because of the existence of several mesomeric structures. The anion is referred to as the phenolate anion. Hence, phenol (2.5) is a weak acid, with a pKa value of 10. This places phenol in between carboxylic acids (pKa = 4-5) and aliphatic alcohols (pKa = 16-19). 

Fluorogenic labelling of pesticides. The subject has been reviewed earlier by Lawrence and Frei (27). Labelling consists in replacing a proton or other atom of a pesticide with a so-called labelling compound such as dansyl chloride (V) or fluores-camine (VI). The former reacts with primary and secondary amines, phenols, some thiols and aliphatic alcohols. The latter reacts very selectively with primary amines. 

Aroma compounds in cured vanilla beans from different countries, e.g. Madagascar, Tonga, Costa Rica, Java, Indonesia and Mexico, have been documented. Over 100 volatile compounds have been detected, including aromatic carbonyls, aromatic alcohols, aromatic acids, aromatic esters, phenols and phenol ethers, aliphatic alcohols, carbonyls, acids, esters and lactones, of which the aldehyde vanillin is the most abundant. The level of the aldehydes, e.g. vanillin and p-hydroxy-benzaldehyde and their respective acids (vanillic acid and p-hydroxybenzoic acid), in cured vanilla beans is used as an indicator of cured vanilla bean quality for commercial purposes (Klimes and Lamparsky, 1976 Adedeji et al., 1993 Ranadive, 1994). 

Phenyl esterase hydrolyzes phenol acid esters (benzoic series) and aliphatic alcohols, such as methyl gallate. 

M.K. Chantooni, Jr. and I.M. Kolthoff, Resolution of acid strength in tert-butyl alcohol and isopropyl alcohol of substituted benzoic acids, phenols, and aliphatic carboxylic acids, Anal. Chem. 51 (1979), pp. 133-140. 

Phosphate plasticizer n. Any of a group of plasticizers derived from phosphoric acid and aliphatic alcohols and phenols, and used in conjunction with others to impart flame resistance. Troitzsch J (2004) Plastics flammability handbook principle, regulations, testing and approval. Hanser-Gardner Publications, New York. Wypych G (ed) (2003) Plasticizer s database. Noyes Publication, New York. 

Most convenient for these studies appeared to be phenols and aliphatic fluorinated alcohols, but for more reactive main group element hydrides the... 

Primary TBDMS ethers can be cleaved selectively in the presence of THP ethers and ketals using ceric ammonium nitrate in methanol. Both phenolic and aliphatic TBDMS ethers undergo cleavage when exposed to catalytic amounts of PdCl2(MeCN)2 in the latter case, and with longer exposure, this also results in oxidation to the corresponding aldehyde or ketone, if the alcohol was primary or secondary, respectively. This cleavage and oxidation can be performed selectively in the presence of TIPS, TBDPS and benzyl ethers (equation 15). 

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