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Organic syntheses - Roger A.

Roger A. Organic syntheses - Chapman, 1936. - 110 p.
Download (direct link): organicsintencis1936.pdf
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2. Notes
1. The temperature should be kept within the limits mentioned to
obtain the best results.
2. The bromine should be added within two hours even though a
small amount may be lost through the condenser.
3. ^-Nitrobenzyl bromide and its solution should be handled with
caution. If the substance comes in contact with the skin, bathing the
affected parts in alcohol will give relief.
4. The inverted filtration method of Bost and Constable (p. 81)
is particularly advantageous for filtering hot solutions of nitrobenzyl
bromide, since it reduces the fire hazard and the manipulation of the
lachrymatory solutions. To avoid dogging, a tube of 8-10 mm. bore must be
used for connecting the filtering flasks. About 3.5 1. of ligroin may be
recovered from the mother liquors.
5. /"-Nitrobenzyl bromide has been used as a reagent for the
identification of many acids 1 and phenols 2 by conversion into their ^-
nitrobenzyl esters and ethers.
3. Methods of Preparation
^-Nitrobenzyl bromide has usually been prepared by bromi-nating ^-
nitrotoluene.1'3 It has also been prepared by treating /(-nitrobenzyl
alcoholjvith hydrobromic acid,4 and by nitrating benzyl bromide.5
1 Reid, J. Am. Chem. Soc. 89,126 (1917); Lyons and Reid, ibid. 39,1728
(1917).
2Reid, ibid. 39, 304 (1917); Lyman and Reid, ibid. 42, 615 (1920).
3 Brewster, ibid. 40, 406 (1918).
4 Norris, Watt and Thomas, ibid. 38,1077 (1916).
* Moureu and Brown, Bull. soc. chim. [4] 29, 1008 (1921).
XIX
no2
/\
NI?
ni
4-NITROPHTHALIC ACID
-/"NcOaH
NH 2I2I
(NaOH) NO2
(HNO3)
\/
C02H
+ NH3
Submitted by E. H. Hontbess, E. L. Shldss, Jr., and P.
Ehrlich. Checked by W. W. Hartman and G. W. Sawdey.
1. Procedure
To a solution of 26.6 g. (0.66 mole) of sodium hydroxide in 240 cc.
of water is added 80 g. (0.416 mole) of 4-nitrophthalimide (p. 58) (Note
1). The mixture is heated rapidly to boiling and boiled gently for ten
minutes. The solution is made barely acid to litmus with concentrated
nitric acid (sp. gr. 1.42); after the neutral point is reached, an
additional 70 cc. (100 g., 1.1 moles) of nitric acid is added (Note 2).
The solution is again boiled for three minutes, then cooled below room
temperature, transferred to a i-l. separatory funnel, and extracted with
two 300-cc. portions of alcohol-free ether (Note 3). Care is taken to
insure thorough mixing before separation of the layers. After drying the
extract over anhydrous sodium sulfate, the ether is distilled off until
solid begins to separate. The concentrated ether solution is poured into
a porcelain dish and the residual solvent allowed to evaporate in a hood
(Note 4). The practically white crystals of 4-nitrophthalic acid which
separate melt at 163-1640 (uncorr.) and have a neutralization equivalent
of 105.5 (theoretical, 105.5). The yield is 85-87 g. (95-99 per cent of
the theoretical quantity).
2. Notes
x. If a large amount of 4-nitrophthalimide is to be hydrolyzed, it
will generally be found convenient to carry out a series of small runs of
the size given here.
66
4-NITROPHTHALIC acid
67
2. The quantity of alkali used at the start is sufficient to
neutralize the nitro-imide and leave the resulting alkaline solution
approximately i N. When the solution is neutralized the red color changes
to a dirty brown, which turns to a pale yellow on acidification. The 70-
cc. portion of concentrated nitric acid suffices to set free all the 4-
nitrophthalic acid but avoids the presence of a large excess during the
ether extraction.
The use of nitric acid appears to be preferable to that of
hydrochloric or sulfuric acid. The yields are similar, but the product
obtained using nitric acid is pure white and in better physical
condition.
3. The simultaneous presence of nitric acid and alcohol in the
ether extract must be avoided as explosive oxidation might occur during
evaporation of the ether. Furthermore, the presence of alcohol may lead
to contamination of the product with traces of the acid ester.
4. Evaporation of the last portion of ether proceeds slowly; the
rather soft, fluffy crystals of acid which separate at first gradually
become hard and dense. No trouble was experienced from nitric acid
remaining with the ether extract, if the ether was free from alcohol and
the specified amount .of nitric acid was used.
3. Methods of Preparation
4-Nitrophthalic acid has usually been prepared by nitration' of
phthalic acid 1 or phthalic anhydride,2'3 followed by separation from the
accompanying 3-nitrophthalic acid.4'5'6 It has also been prepared from 6-
nitro-2-naphthol-4-sulfonic acid (obtained from the technical diazo-
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