Phthalic reagent

The other analytical methods necessary to control the typical specification given in Table 5 are, for the most part, common quality-control procedures. When a chemical analysis for purity is desired, acetylation or phthalation procedures are commonly employed. In these cases, the alcohol reacts with a measured volume of either acetic or phthalic anhydride in pyridine solution. The loss in titratable acidity in the anhydride solution is a direct measure of the hydroxyl groups reacting in the sample. These procedures are generally free from interference by other functional groups, but both are affected adversely by the presence of excessive water, as this depletes the anhydride reagent strength to a level below that necessary to ensure complete reaction with the alcohol. Both procedures can be adapted to a semimicro- or even microscale deterrnination. 

Note Phosphoric acid [8] and hydrochloric acid [6, 9] have both been suggested in the literature as substitutes for phthalic acid. The addition of sodium dithionite [9] is also occasionally mentioned and sometimes no additives are employed [10]. The alternative reagents offer no advantages over the phthalic acid containing reagent since they usually cause more background coloration. The limits of detection are about 0.1 —0.5 pg per chromatogram zone [5]. 

The reduction is general for a variety of substituted benzophenones Such substituents as CH3 OH, OCH3, F, Br. N(CH3)2, NO2. COOH, COOCH3, NHCOC Hreaction conditions and do not alter the course of the reduction Diarylmethanols are reduced to diarylmethanes under the same conditions and probably are the intermediates in the reduction of ketones [26] Triethylsilane also can be used as a reducing agent in trifluoroacetic acid medium [27J This reagent is used for the reduction of benzoic acid and some other carboxylic acids under mild condiUons (equation 14) Some acids (phthalic, sue cinic, and 4-nitrobenzoic) are not reduced under these conditions [27]... 

Dehydration of fi-nitro iilcohols provides an important method for the preparation of nitroalkenes. Because lower nitroalkenes such as nitroethylene, Tnitro-Tpropene, and 3-nitro- Tpropene tend to polymerize, they must be prepared careftdly and used immediately after preparation. Dehydration v/ith phthalic anhydride is the most reliable method for such lower nitroiilkenes. Such lower nitroalkenes have been used as important reagents for Michael acceptors or dienophiles in the Diels-Alder reacdon, which v/ill be... 

Fig. 23 Microwave-promoted SPOS of substituted phthalimides. Reagents and conditions a phthalic acid (R = H, F, Br, CH3, C4H4), DIAD, PPha, THF, rt, 24h b primary amine (R =C3H6Ph, CH(CH3)C2H4Ph, CsH, 4-CH3 0Bn,4-ClBn, C5H9) amine, EDC HCl, HOAt, CH2CI2, rt, 18 h c MW, DMF, 170 °C, 20 min, closed vessel...

Note that these mechanisms are the reverse of those involved in the acid-catalyzed hydration of double bonds (15-3), in accord with the principle of microscopic reversibility. With anhydrides (e.g., P2O5, phthalic anhydride) as well as with some other reagents such as HMPA, it is likely that an ester is formed, and the leaving group is the conjugate base of the corresponding acid. In these cases, the mechanism can be El or E2. The mechanism with AI2O3 and other solid catalysts has been studied extensively but is poorly understood. 

Anthraquinone is widely use in the manufacture of a range of dyes. Two possible routes for manufacturing anthraquinone are (1) from the reaction of 1,4-naphthoquinone with butadiene and (2) reaction of benzene with phthalic anhydride. Describe mechanisms for both these reactions and identify likely reaction conditions and any other reagents required. Compare the atom economy of the two routes. Identify three factors for each route that may influence the commercial viability. 

In some of these syntheses the original reaction conditions were modified and this might partly account for the much shorter reaction times. The synthesis of phthalimidoacetic acid 20 from phthalic anhydride 18 and glycine in the presence of triethylamine (Scheme 4.11) gives a yield of 83-90% when the reagents are heated under reflux in toluene for 1.5 h [29]. Bose found that good yields of the product could be obtained in 1-3 min when the reaction was performed in DMF in a MW oven [18]. 

Phthalazinone, 19 332 o-Phthaldialdehyde-2-mercaptoethanol, chiral derivatizing reagent, 6 76t Phthalein dyes, 19 304-305 Phthalic acid, 19 332... 

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