Functional group addition aromatic compounds

A third example is shown in Fig. 7c. This compound contains a number of weakly basic functional groups, including aromatic and aliphatic amines and pyrimidines, which can be completely deprotonated above approximately pH 8. Because of the high proportion of nitrogen in this molecule (clog P = 0.63), it is fairly polar, yet can be readily extracted from samples with a simple liquid-liquid extraction using common polar organic solvents. Of course, solid-phase extraction could also work well, but would required some additional development time. 

Many pharmacologically active compounds have been synthesized using 5-bromoisoquinoline or 5-bromo-8-nitroisoquinoline as building blocks.6 7 8 9 10 11 The haloaromatics participate in transition-metal couplings 81012 and Grignard reactions. The readily reduced nitro group of 5-bromo-8-nitroisoquinoline provides access to an aromatic amine, one of the most versatile functional groups. In addition to N-alkylation, TV-acylation and diazotiation, the amine may be utilized to direct electrophiles into the orthoposition. 

Since aromatic substitutions, aliphatic substitutions, additions and conjugate additions to carbonyl compounds, cycloadditions, and ring expansion reactions catalyzed by Fe salts have recently been summarized [17], this section will focus on reactions in which iron salts produce a critical activation on unsaturated functional groups provided by the Lewis-acid character of these salts. 

As you learned in Chapter 1, aromatic compounds do not react in the same way that compounds with double or triple bonds do. Benzene s stable ring does not usually accept the addition of other atoms. Instead, aromatic compounds undergo substitution reactions. A hydrogen atom or a functional group that is attached to the benzene ring may be replaced by a different functional group. Figure 2.6 shows two possible reactions for benzene. Notice that iron(III) bromide, FeBrs, is used as a catalyst in the substitution reaction. An addition reaction does not occur because the product of this reaction would be less stable than benzene. 

O Brien. 1235 Ohmic drop, 811, 1089, 1108 Ohmic resistance, 1175 Ohm s law, 1127. 1172 Open circuit cell, 1350 Open circuit decay method, 1412 Order of electrodic reaction, definition 1187. 1188 cathodic reaction, 1188 anodic reaction, 1188 Organic adsorption. 968. 978. 1339 additives, electrodeposition, 1339 aliphatic molecules, 978, 979 and the almost-null current test. 971 aromatic compounds, 979 charge transfer reaction, 969, 970 chemical potential, 975 as corrosion inhibitors, 968, 1192 electrode properties and, 979 electrolyte properties and, 979 forces involved in, 971, 972 977, 978 free energy, 971 functional groups in, 979 heterogeneity of the electrode, 983, 1195 hydrocarbon chains, 978, 979 hydrogen coadsorption and, 1340 hydrophilicity and, 982 importance, 968 and industrial processes, 968 irreversible. 969. 970 isotherms and, 982, 983... 

If compounds already react very fast with ozone, the addition of hydrogen peroxide is nearly ineffective, which was shown by Brunet et al. (1984) in the case of benzaldehyde and phthalic acid. The functional groups on the aromatic ring are relatively reactive towards molecular ozone. The advantage of this process lies in the removal of compounds relatively non-reactive with ozone. It was shown that the oxidation of oxalic acid, which is often an end product in the case of molecular ozone reactions, was significantly accelerated with the addition of hydrogen peroxide. 

The method is simple, and has the additional virtue of great versatility. The requisite ally lie alcohol can be prepared via the Favorskii reaction of a 20-ketopregnane, or via ethoxyacetylene addition to a 17-ketoandrostane. Additional functional groups may be present prior to these reactions or introduced into the A17(20)-compound later. An aromatic A-ring, A-ring unsaturated ketones and the 11 /1-hydroxyl group are all stable to the oxidative attack on the A17(20)-olefln, and the 21-acetate is not hydrolyzed during the reaction. 

Electroenzymatic reactions are not only important in the development of ampero-metric biosensors. They can also be very valuable for organic synthesis. The enantio- and diasteroselectivity of the redox enzymes can be used effectively for the synthesis of enantiomerically pure compounds, as, for example, in the enantioselective reduction of prochiral carbonyl compounds, or in the enantio-selective, distereoselective, or enantiomer differentiating oxidation of chiral, achiral, or mes< -polyols. The introduction of hydroxy groups into aliphatic and aromatic compounds can be just as interesting. In addition, the regioselectivity of the oxidation of a certain hydroxy function in a polyol by an enzymatic oxidation can be extremely valuable, thus avoiding a sometimes complicated protection-deprotection strategy. 

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