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