formaldehyde - Sciencemadness Dot Org

220 FORMALDEHYDE
•with 4 or more mols of formaldehyde, a white rubber-like polymeric product
result* 56 . The course of this reaction is believed TO be quite different from
The ordinary amine aldehyde reactions. In the example cited, one mol of
acetone is liberated for each mol of polyaminonitrile taking part in the
resin-forming reaction.
Amino Acids and Esters
* The reactions of formaldehyde with amino acids and esters are essentially
reactions of the amino group, similar in most respects to those involving the
amines and amine derivatives -which have been already discussed. Of
specific interest in the case of amino acids is the fact that the basicity of the
amino group is reduced by combination with formaldehyde. Schiff's
finding 100 that the lower amino acids, such as glycine, alanine and asparagine.
although practically neutral in ordinary aqueous solution, react as
strong acids in the presence of formaldehyde is the basis for the •well known
Sorenson method 307 for titrating amino acids.
The reactions of glycine (amiao-acetic acid) and its derivatives may be
taken as representative of this group of compounds. In neutral solution
formaldehyde and glycine combine readily, giving methyleneaminoacetie
acid 7s .
XHaCEiCOOH + CH20(aq) ~+ CHa:KGHsCOOH -f- H20
This compound behaves as a normal monobasic acid and may be readily
titrated 57 ' 100 , whereas glycine itself is neutral In strong acid solutions
glycine and formaldehyde react to give methylenediglycine 73 :
2XH.CH.C00H -f CH20 -» H2C{NHCH2COOH)a -f HsO
In the presence of hydrochloric acid and tin, the primary reaction products
of formaldehyde and glycine are reduced to methyl derivatives; sareosme
(methylaminoacetic acid) and dimethylaminoacetic acid are obtained 73 :
XHaCHiCOOH 4- CH*0(aq) +H-- CH3NHCH2COOH -f- H20
CH,>THCH2COOH -f CH.O(aq) 4- H2 -> (CH3)..NCH2COOH H- H30
Although not readily prepared under ordinary conditions, salts of
methylolglycine, H0CHsNHCH2COOH? are formed when solutions of
glyeinates are reacted with formaldehyde at temperatures in the neighborhood
of 0 to o°C fiS . TVhen an excess of commercial formaldehvde solution
is employed and the reaction mixture is not chilled, a compound having
the empirical formula C7Hw05X2 is obtained as the principal product.
According to Krause*, it is probably hydroxytrimethyleneglycine, HOCH
(CH2NHCH2COOH)2. This formula Js supported by the following facts:
(a) it gives a monoacetyl derivative, as would be expected, and (b) acetone