P-Nitrobenzoates

Benzyl p-Nitrobenzoate. N02C H4C00CH2C H6. (Semi-micro Scale.)... 

Thionyl chloride method. Mix 100 g. of pure p-nitrobenzoic acid and 125 g. (77 ml.) (1) of redistilled thionyl chloride in a 500 ml. round-bottomed flask. Fit the flask with a double surface reflux condenser carrying a calcium chloride (or cottou wool) guard tube and connect the latter to an absorption device e.g.. Fig. II, 8, c). Heat the flask on a... 

A large excess of thionyl chloride is recommended in order to avoid the format tion of p-nitrobenzoic anhydride (see Note 1 to Section IV,185). 

Benzocaine (or anaesthesine) is conveniently prep>ared from p-nitrobenzoic acid by either of the following methods ... 

Method 2. Ethyl p-nitrobenzoate. Place 21 g. of p-nitrobenzoic acid (Section IV,154), 11-5 g. of absolute ethyl alcohol, 3 8 g. of concentrated sulphuric acid, and 30 ml. of sodium-dried A.R. benzene in a 250 ml. round-bottomed flask, fit a reflux condenser, and heat the mixture under reflux for 16 hours. Add 50 ml. of ether to the cold reaction mixture, wash the extract successively with sodium bicarbonate soiution and water, dry with anhydrous magnesium sulphate or calcium chloride, and distil off the solvent on a water bath. Remove the last traces of benzene either by heating in an open evaporating dish on a water bath or in a bath at 100-110°. The residual ethyl p-nitrobenzoate (21 g.) solidifies completely on cooling and melts at 56°. 

Determination of melting points (a-naphthylamine, a-naphthol, benzoic acid, succinic acid and p-nitrobenzoic acid). Use the apparatus shown in Fig. II, 10, 2, a. Construction of calibration curve for thermometer. Determination of m.p. of unknown compound. 

A related problem concerns the synthesis of p nitrobenzoic acid Here two meta directing substituents are para to each other This compound has been prepared from toluene according to the procedure shown... 

Hydrolysis of either A or B yields RNHCH2CH2OH and p nitrobenzoic acid Suggest a reason able structure for compound B and demonstrate your understanding of the mechanism of this reaction by wnting the structure of the key intermediate in the conversion of compound A to com pound B... 

NMR, 7, 416 <80JOC4807) Thiane-3-p-nitrobenzoate kinetic data, 3, 902 (74T2087) Thiane-3-p-nitrobenzoate, 3-methyl-kinetic data, 3, 902 <74T2087) Thiane-3-p-nitrobenzoate, 3-phenyl-kinetic data, 3, 902 <74T2087>... 

Thiane-4-p-nitrobenzoate, 4-methyl-kinetic data, 3, 902 (74T2087)... 

Hydrolysis of the ester is achieved by refluxing in aqueous N or 2N NaOH solution until the insoluble ester dissolves. The solution is then cooled, and the alcohol is extracted into a suitable solvent, e.g. ether, toluene or alcohol-free chloroform. The extract is dried (CaS04, MgS04) and distilled, then fractionally distilled if liquid or recrystallised if solid. (The p-nitrobenzoic acid can be recovered by acidification of the aqueous layer.) In most cases where the alcohol to be purified can be readily extracted fi-om ethanol, the hydrolysis of the ester is best achieved with N or 2N ethanolic NaOH or 85% aqueous ethanolic N NaOH. The former is prepared by dissolving the necessary alkali in a minimum volume of water and diluting with absolute alcohol. The ethanolic solution is refluxed for one to two hours and hydrolysis is complete when an aliquot gives a clear solution on dilution with four or five times its volume of water. The bulk of the ethanol is distilled off and the residue is... 

Ethyl p-nitrobenzoate [99-77-4] M 195.2, m 56 . Dissolved in diethyl ether and washed with aqueous alkali, then the ether was evaporated and the solid recrystd from EtOH. 

Isopropyl p-nitrobenzoate [13756-40-6] M 209.2, m 105-106 . Dissolved in diethyl ether, washed with aqueous alkali, then water and dried. Evapn of the ether and recrysln from EtOH gave pure material. 

Various specific experiments support this general scheme. For example, in 80% aqueous acetone, the rate constant for lacemization ofp-chlorobenzhydiyl p-nitrobenzoate (/ ) and that for exchange of label in the carbonyl group can both be measured. At 100 C, kjk = 2.3. 

Steiic effects of another kind become important in highly branched substrates, in which ionization is facilitated by relief of steric crowding in going from the tetrahedral groimd state to the transition state for ionization. The ratio of the hydrolysis rates in 8OV0 aqueous acetone of t-butyl /F-nitrobenzoate and 2,3,3-trimethyl-2-butyl p-nitrobenzoate is 1 4.4. 

The cause of this effect has been called B-strain (back-strain), and in this exanqjle only a modest rate enhancement is observed. As the size of the groups is increased, the effect on rate becomes larger. When all three of the groups in the above example are t-butyl, the solvolysis occurs 13,500 times faster than in the case of t-butyl p-nitrobenzoate. ... 

Table 5.14. Relative Hydrolysis Rates of 2-AU l-2-adamantyl p-Nitrobenzoates"...

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