Hydroxyl group alkylation

Hydroxyl-substituted naphthimidazoles, benzothiazoles, benzimidazoles, benzotriazoles, benzoselenazoles and benzoxathiolones may be regarded as substituted phenolic couplers. Compound (121) is a specific example of the latter type which yields intense brown images (51USP2547843). In the absence of hydroxyl groups, alkyl-substituted derivatives of imidazoles or thiazoles may be couplers in their own right by virtue of their active alkyl substituent. 

R polymeric backbone containing hydroxyl group alkyl hydrophobe X halogen atom... 

Substitution at the C-3 carbon of malic acid primarily involves alkylation reactions. In contrast to alkylations at the C-2 carbon (Section 3.2.2.2), which require prior manipulation of the 1-carboxyl and hydroxyl groups, alkylation at the C-3 carbon c be performed directly on malic acid esters. ... 

Functional class names of alcohols are derived by naming the alkyl group that bears the hydroxyl substituent (—OH) and then adding alcohol as a separate word The chain IS always numbered beginning at the carbon to which the hydroxyl group is attached... 

Hydroxyl groups take precedence over ( outrank ) alkyl groups and halogen substituents m determining the direction m which a carbon chain is numbered The OH group is assumed to be attached to C 1 of a cyclic alcohol and is not numbered... 

Selectivity is not an issue m the conversion of alcohols to alkyl halides Except for certain limitations to be discussed m Section 8 15 the location of the halogen sub stituent m the product corresponds to that of the hydroxyl group m the starting alcohol... 

Alkyl sulfonates are derivatives of sulfonic acids m which the proton of the hydroxyl group is replaced by an alkyl group They are prepared by treating an alcohol with the appropriate sulfonyl chloride usually m the presence of pyridine... 

Alkylation (Section 25 22) Alkyl halides react with carbohydrates to form ethers at the available hydroxyl groups An application of the Williamson ether synthesis to carbohydrates... 

The hydroxyl groups can be alkylated with the usual alkylating agents. To obtain aryl ethers a reverse treatment is used, such as treatment of butynediol toluenesulfonate or dibromobutyne with a phenol (44). Alkylene oxides give ether alcohols (46). 

The hydroxyl groups can be alkylated in the usual manner. Hydroxyalkyl ethers may be prepared with alkylene oxides and chloromethyl ethers by reaction with formaldehyde and hydrogen chloride (86). The terminal chlorides can be easily converted to additional ether groups. 

The hydroxyl groups on glycols undergo the usual alcohol chemistry giving a wide variety of possible derivatives. Hydroxyls can be converted to aldehydes, alkyl hahdes, amides, amines, a2ides, carboxyUc acids, ethers, mercaptans, nitrate esters, nitriles, nitrite esters, organic esters, peroxides, phosphate esters, and sulfate esters (6,7). 

A nitro alcohol is formed when an ahphatic nitro compound with a hydrogen atom on the nitro-bearing carbon atom reacts with an aldehyde in the presence of a base. Many such compounds have been synthesized, but only those formed by the condensation of formaldehyde (qv) and the lower nitroparaffins (qv) are marketed commercially. The condensation may occur one to three times, depending on the number of hydrogen atoms on the nitro-substituted carbon (R and R = H or alkyl), and yield nitro alcohols with one to three hydroxyl groups. 

Organochromium Catalysts. Several commercially important catalysts utilize organ ochromium compounds. Some of them are prepared by supporting bis(triphenylsilyl)chromate on siUca or siUca-alumina in a hydrocarbon slurry followed by a treatment with alkyl aluminum compounds (41). Other catalysts are based on bis(cyclopentadienyl)chromium deposited on siUca (42). The reactions between the hydroxyl groups in siUca and the chromium compounds leave various chromium species chemically linked to the siUca surface. The productivity of supported organochromium catalysts is also high, around 8—10 kg PE/g catalyst (800—1000 kg PE/g Cr). 

The aromatic ring of alkylphenols imparts an acidic character to the hydroxyl group the piC of unhindered alkylphenols is 10—11 (2). Alkylphenols unsubstituted in the ortho position dissolve in aqueous caustic. As the carbon number of the alkyl chain increases, the solubihty of the alkah phenolate salt in water decreases, but aqueous caustic extractions of alkylphenols from an organic solution can be accomphshed at elevated temperatures. Bulky ortho substituents reduce the solubihty of the alkah phenolate in water. The term cryptophenol has been used to describe this phenomenon. A 35% solution of potassium hydroxide in methanol (Qaisen s alkah) dissolves such hindered phenols (3). 

Hydroxyl Group. Reactions of the phenohc hydroxyl group iaclude the formation of salts, esters, and ethers. The sodium salt of the hydroxyl group is alkylated readily by an alkyl hahde (WiUiamson ether synthesis). Normally, only alkylation of the hydroxyl is observed. However, phenolate ions are ambident nucleophiles and under certain conditions, ring alkylation can also occur. Proper choice of reaction conditions can produce essentially exclusive substitution. Polar solvents favor formation of the ether nonpolar solvents favor ring substitution. 

The reactions of thionyl chloride with organic compounds having hydroxyl groups are important. Alkyl chlorides, alkyl sulfites, or alkyl chlorosulfites form from its reaction with aUphatic alcohols, depending on reaction conditions, stoichiometry, and the alcohol stmcture ... 

In the olivanic acid series of carbapenems the ( )-acetamidoethenyl grouping can be isomerised to the (Z)-isomer (19) (22) and reaction with hypobromous acid provides a bromohydrin that fragments to give a thiol of type (20) when R = H, SO H, or COCH. The thiol is not isolated but can react to provide new alkyl or alkenyl C-2 substituents (28). In the case of the nonsulfated olivanic acids, inversion of the stereochemistry at the 8(3)-hydroxyl group by way of a Mitsunobu reaction affords an entry to the 8(R)-thienamycin series (29). An alternative method for introducing new sulfur substituents makes use of a displacement reaction of a carbapenem (3)-oxide with a thiol (30). Microbial deacylation of the acylamino group in PS-5 (5) has... 

The effect substitution on the phenolic ring has on activity has been the subject of several studies (11—13). Hindering the phenolic hydroxyl group with at least one bulky alkyl group ia the ortho position appears necessary for high antioxidant activity. Neatly all commercial antioxidants are hindered ia this manner. Steric hindrance decreases the ability of a phenoxyl radical to abstract a hydrogen atom from the substrate and thus produces an alkyl radical (14) capable of initiating oxidation (eq. 18). 

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