The nucleophilic halogenalkylation reactions of propylene oxide with halogenmethane anion (CH 2 X -) and dihalogenmethane anion (CHX -2 ) (X = F, Cl) in the gas phase and in the Et 2 O solvent are studied using the B3LYP method and the SCIPCM model for simulating solution effects. Our calculations predict the same reaction path for following reactions: (1) (X = F, Cl) and (2) (X = F) in the two phases, but there is a little difference in the relative energy of IM1(2Cl) in the gas phase and in the Et 2 O solvent for reaction (2) (X = Cl). All the four reactions proceed in two steps. Reactions (1) and (2) are predicted to be exothermic and thermodynamically favourable in both the gas phase and the Et 2 O solvent. The overall barrier energies for reaction (1) (X = F), reaction (1) (X = Cl), reaction (2) (X = F), and reaction (2) (X = Cl) are predicted to be 2⋅74 and 4⋅08 kcal mol -1 , 3⋅35 and 5⋅20 kcal mol -1 , 4⋅67 and 6⋅05 kcal mol -1 , and 5⋅33 and 8⋅23 kcal mol -1 in the gas phase and in the Et 2 O solvent, respectively. The accurate calculation of results for the model systems would be useful for experimental researchers working in this field.
The small molecules already existing on the earth can be assembled to biological macromolecules in the presence of the suitable tool. A workman must sharpen his tools if he is to do his work well. The tool must be specific, delicate and automatic. Obviously, it is enzyme. Therefore, to explore the origin of life we must understand the origin of the manufacturing tool of biological macromolecules--the origin of enzymes. We can understand more about the origin and evolution procedures of enzymes from the NO2. NO2 can easily form the dimmer, N2O4. Four N2O4 molecules can coordinate with a suitable metal ion and form a plane super molecule with four N2O4 molecules. This supramolecule provides the basis for the appearance of enzymes: (1) It is the template for producing enzymes. (2) It provides the active centers for enzymes. (3) It provides for the enzymes with specific function of chiral selection. This supramolecule reacts with formaldehyde and porphyrin compound is gradually formed. Once suitable function groups are substituted on the porphyrin ring, enzymes are formed. The primitive environment of earth can easily produce NO2 and CH2O. Therefore, this might be one clue to the origin of life.
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