S. DILLI AND J. H. GREEN 



chosen to resemble present concepts of primitive conditions on earth. He 

 assumed a reducing atmosphere, that the surface of the earth was mainly 

 ocean and that reactions occurred below 100°C as a result of excitation and 

 ionization from lightning discharges. Miller subjected a mixture of ammonia 

 (or nitrogen), methane, water vapour and hydrogen to a silent electrical 

 discharge for periods of up to a week. The products were analysed chromato- 

 graphically and sometimes the pure products were isolated and identified 

 by standard methods. These procedures seem to have been adequate except 

 for the purines and pyrimidines which were sought on paper chromatograms 

 scanned with u.v. light. However, these compounds do not absorb in the 

 u.v. region and, in any case, they might be expected in reduced forms-^ for 

 which Miller did not search. 



The general conclusion which can be reached is that, if HCN and aldehydes 

 are present, the Strecker cyanohydrin synthesis reaction provides a pathway 

 to amino and hydroxy acids: 



RCHO + NH3 + HCN > RCH (NHg) CN + HgO 



RCH(NH2)CN + 2H2O > RCH(NH2)COOH + NH3 



or 



RCHO + HCN RCH(OH)CN 



RCH(OH)CN + 2H.,0 > RCH(OH)COOH + NH3 



In his most recent work, Miller verified that these reactions do occur at 

 100°C under the conditions which have been taken to apply to primitive 

 processes. He boiled for a week a mixture of the following compounds: 

 Hydrogen at 30 cm pressure, 4-5 ml. 28 per cent ammonia (corresponding 

 to 25 cm pressure), 20 mmoles hydrogen cyanide, 6 • 1 mmoles formaldehyde, 

 3-64 mmoles acetaldehyde and 1-16 mmoles propionaldehyde in 325 ml. 

 water. The following products were found in percentage yields, based on 

 aldehyde added, which are in parenthesis — glycine (16), alanine (35), 

 a-aminobutyric acid (23), glycolic acid (12), lactic acid (12), a-hydroxy- 

 butyric acid (13), iminodiacetic acid ( 1 8) and imino-acetic-propionic acid (?) . 



In the actual syntheses which Miller made, he found that the replacement 

 of ammonia by nitrogen produced the same products but the yield (based 

 on carbon in the original mixture) dropped from 15 to 7 per cent. (Another 

 interesting point is that the presence of ferrous iron, which might be expected 

 if there were much iron present at the formation of the planets, did not 

 increase the yield.) The compounds which were formed in the greatest 

 yield — quantities are quoted in the parentheses as moles x 10^ — and which 

 were definitely identified were as follows: 



(a) Amino acids and derivatives — Glycine (63), ^,/-alanine (34), saixosine 

 (5), j3-alanine (15), a-aminobutyric acid (5), N-methylalanine (1), aspartic 

 acid (0-4j, glutamic acid (0-6), iminodiacetic acid (5-5) and imino-acetic- 

 propionic acid (methyl ethylamine a, a^-dicarboxylic acid) (1 -5). 



(b) Hydroxy acids — Glycolic acid (56), lactic acid (31) and a-hydroxy- 

 butyric acid (5). 



(c) Aliphatic acids — Formic acid (233), acetic acid (15-2), propionic acid 

 (12-6) and succinic acid (3-8). 



(d) Ureas — Urea (2) and methylurea (1 -5). 



109 



