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J. Chem. Eng. Data 2010, 55, 5302–5304
Solubilities of 2,4-Dinitro-L-phenylalanine in Monosolvents at (273.15 to 368.15) K
Jin-Qiang Liu,†,‡ Chao Qian,*,† and Xin-Zhi Chen†
Department of Chemical and Biotechnological Engineering, Zhejiang University, Hangzhou 310027, P. R. China, and College of
Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, 471022, P. R. China
The solubilities of amino acid, 2,4-dinitro-L-phenylalanine in monosolvents water, methanol, ethanol,
1-propanol, 2-propanol, 1-butanol, 2-butanol, acetone, ethyl acetate, and 1,2-dichloroethane were measured
from (273.15 to 368.15) K at atmospheric pressure using the synthetic method. The solubility was determined
by a laser monitoring observation technique. The experimental solubilities were regressed by the modified
Apelblat equation with the relative deviation less than 2.5 %.
Introduction
Experimental Methods
Chemicals. 2,4-Dinitro-L-phenylalanine, not commercially
available and synthesized from the nitrition of L-phenylalanine
following a procedure similar to that of Almog7 employing urea
nitrate as the nitrating agent, was twice recrystillized from
1-propanol with a melting point of (191.5 to 192.4) °C (dec.).
The 2,4-dinitro-L-phenylalanine thus obtained had a mass
fraction purity greater than 0.998, and the structure was
The solubility of an uncombined substance is an important
property, characterizing and quantitatively defining certain
inherent properties. It depends, however, not only upon proper-
ties of the liquid phase but also upon those of the substances in
the solid state.1 Recent advances in the biochemical industry
draw much attention to the development of more sophisticated
and efficient processes for the separation, concentration, and
purification of biomolecules. Amino acids are the simplest
biomolecules, and the solubility of unnatural amino acids that
can be utilized as food additives and constituents of pharma-
ceutical products is of great importance.
confirmed with H NMR and 13C NMR. H NMR (400 MHz,
D2O) δ (ppm): 8.85 (d, 1H, 3-H, J ) 2.0 Hz), 8.38 (dd, 1H,
5-H, J ) 2.0, 8.4 Hz), 7.63 (d, 1H, 6-H, J ) 8.4 Hz), 3.99 (t,
1H, -CH-, J ) 7.6 Hz), 3.48 (ddd, 2H, -CH2-, J ) 7.2, 8.0,
14.0 Hz). 13C NMR (101 MHz, D2O) δ: 170.23, 149.07, 148.29,
132.99, 131.80, 128.21, 122.60, 51.85, 35.77. Deionized water
(with the electrical conductivity of < 3·10-6 S) was used in
our experiment. Organic solvents (99.8 % in mass fraction) were
purchased from Hangzhou Chemical Reagent Co., Ltd. of China
and distilled before use. The purity of the 2,4-dinitro-L-
phenylalanine was based on the 1H NMR spectrum and HPLC.
Apparatus and Procedure. The solubility of a solid in a
solvent was measured following the method reported in the
literature.6 In our previous work,8 our co-worker had explained
the procedure in detail, and little improvement was made.
All the apparatuses including composition and type were exactly
the same as with our previous work. So, here, we described it
briefly. Our solubility apparatus included a 200 mL jacketed
glass vessel, a thermostat, a magnetic stirrer, and a mercury-
in-glass thermometer (uncertainty of ( 0.05 K). A laser beam
was employed to observe the dissolution of the solid + liquid
mixture. The light signal transmitted through the vessel was
collected by a detector to guarantee the dissolution of the last
crystal, and the equilibrium point of the given system was
estimated on the basis of the signal change.
1
1
2,4-Dinitro-L-phenylalanine is a special one because its
derivatives of three stereoisomers of diaminopimelic acid (DAP),
which was thought to be mainly synthesized by bacteria
incorporated in the peptidoglycan of bacterial cell walls,2 were
successfully separated with HPLC,3 and the phenylalanine
residue in protein could lead to a dramatic increase in both
solubility and stability for its hydrophobicity.4 However, pure
2,4-dinitro-L-phenylalanine has not been obtained yet in the
literature. It is an important intermediate in our synthesis of
indoline-2-carboxylic acid. It was obtained from the successive
nitration of L-phenylalanine, and to find a suitable solvent for
its recrystillization, its solubility was measured in different
solvents including water, methanol, ethanol, 1-propanol, 2-pro-
panol, 1-butanol, 2-butanol, acetone, 1,2-dichloroethane, and
ethyl acetate. They may be useful for the separation and scale-
up.
There are two methods to measure solubility: the analytic
method and the synthetic method.5 In the analytic method, all
the materials are stirred together at a given temperature for a
certain time, and then the upper solution is analyzed after the
stirring stops for some time and the concentration of solute
considered as the solubility at the temperature. In the synthetic
method, the amount of the materials is known, and the solubility
can be determined by observing the disappearance of the solid
phase. Recently, the laser technique has been widely used to
monitor the solution of the solid and get the solubility data.6
At the beginning of each experiment, a known mass of solute
determined by an electronic analytical balance (type BS210S,
Sartorius Scientific Instrument Co. Ltd.) with an uncertainty of
less than 0.0001 g was added to a known mass of solvent at a
known temperature. The undissolved solid particles were
completely suspended in the jacketed vessel by continuous
stirring for 60 min, and then a quantitative additional solvent
was added into the vessel through a buret. The intensity of the
penetrated light increased with the increase of the amount of
solvent in the vessel, and the penetrated light intensity reached
* Corresponding author. E-mail: chemtec@163.com.
† Zhejiang University.
‡ Luoyang Normal University.
10.1021/je100352r 2010 American Chemical Society
Published on Web 08/10/2010