constituents highest energy acids and bases dehydration reaction chemical reactions catalytic hydrogenation catalyst metabolism hydrogen bonds organic solvents oxidation amino acids concentration alcohols phosphate atom esters transition state organic chemistry dna molecule atomic weights correlation hydrogen gas carbon atoms carbon dioxide alkyne dehydration chemistry acyl glucose electrons exothermic reaction reactants racemic mixture protons chromosomes atoms chemicals alkenes salicylic acid cells cytosine pyruvate nucleophile joules ethers thymine chirality sodium atomic mass protons neutrons and electrons junior chemistry diels alder reaction carbons molecules living organisms electrophile reagents byproducts proteins molecule ketone synthesis organic reactions isomer equilibrium hydrogen peroxide krebs cycle temperatures cesium local anesthetic electron acceptor electron pair Organic derivatives alkene cis catalysts methanol aspirin selectivity single step intermediates journal article covalent bonds ammonia reagent substrates acetone presence water molecules hydrogen alcohol heat flow cell cycles electron density activation energy room temperature chemical reaction solvent