Acids and substitution

A number of studies of the acid-catalyzed mechanism of enolization have been done. The case of cyclohexanone is illustrative. The reaction is catalyzed by various carboxylic acids and substituted ammonium ions. The effectiveness of these proton donors as catalysts correlates with their pK values. When plotted according to the Bronsted catalysis law (Section 4.8), the value of the slope a is 0.74. When deuterium or tritium is introduced in the a position, there is a marked decrease in the rate of acid-catalyzed enolization h/ d 5. This kinetic isotope effect indicates that the C—H bond cleavage is part of the rate-determining step. The generally accepted mechanism for acid-catalyzed enolization pictures the rate-determining step as deprotonation of the protonated ketone ... 

Use the initial concentration of C032-for the base and that of HCO for the acid and substitute the values of pH and pKa. 

In their approach toward luotonin A analogues, which are inhibitors of topoisomerase I, Hecht and co-workers reacted pyrroloquinoline 269 with a range of anthranilic acids and substituted thiophenes such as 270 to give 271 (Equation 73) <2004BMC6287>. 

As mentioned in the introduction, 3-hydroxy fatty acids with functional groups can also be incorporated in poly(3HAMCL). Table 2 illustrates this with many examples of alkenes, 3-hydroxyalkenoic acids, and substituted 3-hy-droxyalkanoic acids that are readily integrated in poly(3HAMCL). Long chain fatty acids have also been used successfully as substrates for poly(3HAMCL) production. De Waard et al. [44] used oleic acid and linoleic acid to produce... 

Brittelli, D.R., Preparation of Dialkyl- and Diarylphosphonoalkanoic Acids and Substituted Acrylic Acids, U.S. Patent 4,307,232, 1981. 

We now turn to substituent-sensitive tautomerism. Johnson and Rumon studied a series of solids derived by cocrystallizing substituted benzoic acids and substituted pyridines (108). Their IR evidence indicated, as expected, that when the benzoic acid is a strong acid and the pyridine a strong base, salts 50a are formed. For a weak acid and a weak base, hydrogen-bonded pairs of neutral molecules,... 

This group of pesticides comprises different families of chemicals with her-bicidal action including substituted phenols, chlorinated aliphatic acids, chloro-phenoxy alkanoic acids, and substituted benzoic acids, which possess carboxyl or phenolic functional groups capable of ionization in aqueous media to yield anionic species [47,151,168-170]. 

The loss of CO2 appecirs in the spectra of many diccirboxylic acids and substituted carboxylic acids. Aromatic acids often exhibit a prominent OH loss followed by CO loss. For excimple, in acid anhydrides, a break may occur on either side of the connecting oxygen atom, and this is followed by the loss of CO. 

In halogenation, halogen atoms are substituted for hydrogen atoms. The process of nitration produces a number of nitro compounds, for example, nitroglycerin. Nitration involves the reaction between benzene and nitric acid in the presence of sulfuric acid. During the reaction, the nitronium ion, NO +, splits off from nitric acid and substitutes on to the benzene ring producing nitrobenzene ... 

The strategy used to prepare the analogue, trixosalen (4-6), differs in the order in which the heterocycfic rings are built. Condensation of malonic acid and substituted... 

The reaction of verdazyls (111) with diacyl peroxides, such as benzoyl peroxide, dilauroyl peroxide, perbenzoic acid and substituted perbenzoic acids has received considerable attention (76TL1893, 78ZOR2471, 78MI22101). One mole of the radical always consumes three moles of the peroxide. The first product is the verdazylium salt (113) which is then transformed into the Af-formylformazan (112). 

Das S, von Sonntag C (1986) Oxidation of trimethylamine by OH radicals in aqueous solution, as studied by pulse radiolysis, ESR and product analysis. The reactions of the alkylamine radical cation, the aminoalkyl radical and the protonated aminoalkyl radical. Z Naturforsch 41b 505-513 Dixon WT, Norman ROC, Buley AL (1964) Electron spin resonance studies of oxidation. Part II. Aliphatic acids and substituted acids. J Chem Soc 3625-3634 Draper HH, Squires EJ, Mahmoodi H, Wu J, Agarwal S, Hadley M (1993) A comparative evaluation of thiobarbituric acid methods for the determination of malondialdehyde in biological materials. Free Rad Biol Med 15 353-363... 

The products obtained from esters of anthranilic acid and substituted anthranilic acids are of interest because fluorenones can be prepared from them. From diazotized methyl anthranilate and benzene, 2-carbometh-oxybiphenyl is obtained in 24% yield. Hydrolysis affords 2-biphenylcar-boxylic acid, which can be cyclized to fluorenone. By this procedure, a number of 2- and 3-substituted fluorenones have been prepared.16 Thus, 3-chlorofluorenone was prepared from methyl 4-chloroanthranilate and benzene through the following steps. 

Frank and coworkers (14) dimerized butadiene, styrene, and a-methylstyrene with finely dispersed sodium metal to give sebacic acid and substituted adipic acids, respectivdy, in good yields. In the case of butadiene, a portion of the product was a substituted suberic acid. Styrene and a-methylstyrene (14a) gave, on termination with water, about 90% yields of 1,4-diphenylbutane and 2,5-diphenylhexane, respectively. 

Diaminodiphenyl sulphone and related drugs are chromatographed as 4,4 -diiodo derivatives. The amino groups are diazotized by treatment with nitrous acid and substituted with iodine, and the resulting derivative provides a high ECD response [568]. 

In alkaline solutions, xanthine alkylates on nitrogen in the order N-3, N-7, N-1, i.e. in decreasing order of acidity, and substitution is easier when the first position has been alkylated so to this extent dialkyl derivatives tend to be most easily produced. Thus 3,7-dimethylxanthine (theobromine) is produced by methylation of xanthine or 3-methylxanthine with methyl iodide and barium carbonate (33JCS662) or dimethyl sulfate in potassium hydroxide at 60 °C (50CB201). However when the oxygen functions are blocked by trimethylsilylation, alkylation occurs at N-7 (64CB934). 

Other interesting condensation i)roducts are those between sodium p-arsanilie acid and substituted benzyl chlorides, phehoxyethyl bromide, and phenacyl halides, which lead, respectively, to the following types of compounds ... 

Branched-chain acids and substituted acids are named as derivatives of the straight-chain acids. To indicate the position of attachment, the Greek letters, a-, etc., are used the a-carbon is the one bearing the carboxyl group. 

One of the most valuable methods of preparing carboxylic acids makes use of ethyl malonate (malonic ester), CH2(COOC2H5)>, and is called the malonic ester synthesis. This synthesis depends upon (a) the high acidity of the a-hydrogens of malonic ester, and (b) the extreme ease with which malonic acid and substituted malonic acids undergo decarboxylation. (As we shall sec, this combination of properties is more than a happy accident, and can be traced to a single underlying cause.)... 

The reactions of carboxylic acids and substituted acids with the titanous-peroxide system have been studied by Dixon et al. (1964). The acids are less reactive than alcohols for example, whereas the. signals ascribed to the oxidizing radicals are eliminated by an approximately O 1m solution of methanol, acetic acid is required in about 2 m concentration the radicals resulting are -CHg. CO2H and, in lower concentration, CH3. The main lines in the spectrum from propionic acid are those of the radical formed by abstraction from the ]8-carbon atom. 

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