4-Nitro-benzoic acid temperatures

Hydrolysis of methyl m-nitrobenzoate to m-nitrobenzoic acid. Place 90 6 g. of methyl m-nitrobenzoate and a solution of 40 g. of sodium hydroxide in 160 ml. of water in a 1-litre round-bottomed flask equipped with a reflux condenser. Heat the mixture to boiling during 6-10 minutes or until the ester has disappeared. Dilute the reaction mixture with an equal volume of water. When cold pour the diluted reaction product, with vigorous stirring, into 125 ml. of concentrated hydrochloric acid. Allow to cool to room temperature, filter the crude acid at the pump and wash it with a little water. Upon drying at 100°, the crude m-nitro-benzoic acid, which has a pale brownish colour, weighs 80 g. and melts at 140°. Recrystallisation from 1 per cent, hydrochloric acid affords the pure acid, m.p. 141°, as a pale cream solid the loss of material is about 5 per cent. 

In order to demonstrate the versatility of the immobilized 4-fluoro-3-nitro benzoic acid scaffold 10, we also synthesized benzopiperazinones derivatives. The building block used for the synthesis of benzopiperazinones is shown in Fig. 14. Complete acylation of 12 at the secondary aniline site was achieved by a reaction with chloroacetyl chloride in the presence of triethyl amine. Finally, one pot intramolecular cyclization of 25 and cleavage was done with NaOMe/ MeOH at room temperature. According to the thin layer chromatography analy-... 

Thus, the reaction of alkyl halides and a-halo esters with sodium nitrite provides a very useful synthetic method for nitroalkanes and a-nitro esters. However, ethyl bromoacetate is exceptional in that it fails to give ethyl nitroacetate on treatment with sodium nitrite.93 This is due to the acidic hydrogen of the ethyl nitroacetate, which undergoes a further reaction with sodium nitrite to give the oxidized products (see Section 6.1, which discusses the Nef reaction). In a similar way, the reaction of benzyl bromide with sodium nitrite at 25 °C gives benzoic acid predominantly. To get phenylnitromethane, the reaction must be carried out at low temperature (-16 °C) (Eq. 2.48).93... 

Lutski directed attention to the H bond in simpler molecules by proposing that the influence of ethanol solvent on the UV spectrum of an orthoh.y6.voxy keto- or nitro aromatic provides a criterion for an j n/ramolecular H bond (1287, 1285). Brieglieb and Strohmeier were able to detect the influence of H bonded dimer formation on the spectra of acetic acid vapor at different temperatures (near 2100 A) (279). There have followed many valuable studies directed at the effect of H bonding on the electronic transitions of acids such as phenols, aniline (1483, 1481, 2056), benzoic acid and derivatives (2076, 1998, 671, 190), acetanilides (2075, 2074), HF (1771, 1770), naphthols (1479, 1484), sulfinic acids (521), and amides (1436). The most extensive work, that of Nagakura, Baba, and co-workers, is of particular importance because it led to theoretical consideration of the nature of the H bond (see Section 8.3.2). (See adso 2056,. 1418, 1850.)... 

Copper powder-Benzolc acid (b.p. 249°). Smith found that chlorine can be reductively removed from aromatic nitro-chioro compounds by treatment with copper powder in molten benzoic acid at 150-200°. The hydrogen presumably is provided by the carboxyl group of the acid. 2,4-Dinitro-l-chloronaphthalene afforded 1,3-dinitro-naphthalene in 74% yield. Newman, who applied this method to 4-bromo- and 4-iodo-2,5,7-lrinitrofluorenone and obtained 2,5,7-trinitrofluorenone in yields of 78 and 22%, recommends Extra fine copper No. 5143, O. Hormmel Co., Pittsburgh, Pa., and states that the temperature is critical and should be in the range 170-180° (internal). 

Oxalyl chloride (reaction c) is more reactive than phthaloyl chloride and its use enables the chlorides to be obtained from sensitive carboxylic acids1116 or their Na salts in benzene1117 at ambient temperature or below. Some of the nitro derivatives of benzoic acid afford only the mixed anhydrides when 2 moles of the acid are heated with 1 mole of oxalyl chloride.1118 To obtain the free acid chloride, and not its hydrochloride, from basic carboxylic acids an alkali salt of this acid may be treated with oxalyl chloride. 

Reductions. Lane has reviewed reductions with BMS. He notes that this reagent is somewhat less reactive than BH3 THF and usually requires a temperature of 20-25°. He recommends that the reagent be added at this temperature. Reduction of aliphatic carboxylic acids proceeds readily, but reduction of benzoic acids is slow unless trimethyl borate is added. The reagent reduces acids, esters, oximes, nitriles, and amides, but does not reduce halides or nitro groups. 

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