Formation of Organic Compounds 93 



hydes and hydrogen cyanide would have contributed to the amount of a-amino 

 acids in the hydrosphere of the primitive Earth. Therefore, electric discharges 

 are not critical for the synthesis of amino acids, and similar results could be 

 expected from ultraviolet light. 



The ultraviolet light emitted by the sun as black-body radiation amounts to 

 85 cal cm"2yr~i for wavelengths less than 2000 A and i-6 cal cm~2yr-i for 

 wavelengths less than 1500 A [4]. Superimposed on the black-body radiation is 

 a strong Lyman a-line at 1216 A of 1-9 cal cmr^ yr~i [13], This line is absorbed 

 by CH4, H2O, NH3 and CO. 



Hydrogen atoms from photolysis of CH4, NH3 and H2O would react with 

 CO to give formaldehyde [14, 15]. Carbon monoxide activated by wavelengths 

 less than 1545 A reacts with H2 to give formaldehyde and glyoxal [16]. Hydroxyl 

 radicals would react with hydrocarbons to give aldehydes [17]. If any O atoms 

 should be formed by photolysis of water or CO, they would react rapidly with 

 H2 to give H2O and with hydrocarbons to give aldehydes*. 



Active nitrogen, probably N atoms in the ^S state [18, 19], reacts with methane 

 and other hydrocarbons to give hydrogen cyanide in good yield [20]. Photo- 

 dissociation of N2 (>iiooA) or NH radicals give N atoms. NH and NH2 

 radicals from the photolysis of ammonia might react with hydrocarbons to give 

 hydrogen cyanide, but this has not yet been demonstrated. 



The reactions outlined above show that aldehydes and hydrogen cyanide 

 would be produced photochemically, and there probably are other photochemical 

 reactions that would also give these compoundsf. 



Infra-red radiation by the polyatomic molecules of the reducing atmosphere 

 would probably result in a cool atmosphere and ocean rather than the boiling 

 temperatures used in these experiments or the molten Earth proposed by some 

 workers. However if there were any local areas of high temperature, hydrogen 

 cyanide would be formed [21], and aldehydes might be synthesized from hydro- 

 carbons and carbon monoxide by reactions analogous to the Fischer-Tropsch 

 or hydroformalation reactions [22]. 



If the conditions on the Earth were cool, then the hydrolysis of the nitriles 

 would still take place, but more slowly than in these experiments. The Strecker 

 synthesis of amino acids will work at much lower concentrations of aldehyde 

 and hydrogen cyanide than obtained in these experiments. At very low concen- 

 trations, however, the Strecker synthesis will not operate. The rate of synthesis 

 of amino acid is given by 



- d (HCN)/d? = kK (NH3) (RCHO) (HCN) 



* If aldehydes were synthesized from the Lyman a-radiation with a quantum yield 

 of I -o, then yield for the Earth would be 2 • 10^'' moles yr-^. If the aldehydes were dissolved 

 in the present oceans this would give a solution of 3 • 10-* m. Of course, the efficiency 

 of the Lyman radiation would not have been 100%, but the oceans would probably 

 have been smaller in volume, and the electric discharges and temperature reactions 

 would contribute to the aldehyde production. 



t Some preiiminarv experiments performed at Brookhaven National Laboratory 

 showed that the 1850 A mercury Une will synthesize amino acids from CH4, NH3, and 

 H..O. Only NH3 and H2O absorb this line but apparently the radical reactions formed 

 the active carbon intermediates. Formaldehyde was detected. The yield of amino acids 

 was very low. 



