Table 1.
Standard free energy of reactions (ΔrG° in kJ mol−1) of simple carbon derivatives susceptible to giving rise to early metabolisms. Values in parentheses are published by Urey in 1952 [29].
| compound | oxidation with O2 to CO2 and H2O | reduction with H2 to CH4 and H2O | disproportion to CH4, CO2 and H2O | reduction with H2 to -CH2-a and H2O | conversion to -CHOH-b,c | carbonization to graphite, H2O and H2 |
|---|---|---|---|---|---|---|
| CO2 (g) | 0 | −130 (−131) | 0 | −74 | +6 | n.a. |
| HCOOH (l) | −270 (−296) | −163 (−189) | −66 (−91) | −107 | −27 | n.a. |
| CH2O (g) | −529 (−522) | −185 (−178) | −120 (−113) | −129 | −49 | −135 |
| CH3OH (l) | −702 (−707) | −121 (−126) | −88 (−93) | −65 | +15 | −70 |
| CH4 (g) | −818 (−818) | 0 | 0 | n.a. | +136 | +50 |
| –CHOH– (l)b | −480 | −136 | −71 | −80 | 0 | −86 |
| –CH2– (l)a | −630 | −49 | +4d | 0 | +80 | +1 |
| C (graphite) | −394 | −50 | +15d | +6 | +86 | 0 |
aAs a methylene group in pentanoic acid compared with butanoic acid, ΔfG°(–CH2–) = −1 kJ mol−1.
bAs –CHOH– group in glycerol compared with ethylene glycol, ΔfG°(–CHOH–) = −151 kJ mol−1.
cBy hydration, hydrogenation or dehydrogenation involving H2 and/or H2O as reagents or products as necessary.
dWater is consumed (instead of being produced).