ORGANIC STRUCTURE : CHEMICAL 27 



These three substances are all C5H12, but they are all different 

 in chemical properties. 



(2) Consider the " carbon-ring " 



H 



C 



H - C-^^C - H 



I !| (which is benzene) 



H — C^ /C — H 

 C 



H 



and suppose three of the — H's replaced by — OH's : there are 

 three different substances formed in this wav. Thus 



OH OH OH 



C C C 



H-C^^C-OH H-C^^C-H H-C-^^C-OH 



H-C\/C-OH, OH-C^/C-OH, H-C^^^C-H 



c c c 



H H OH 



although each contains the same numbers of —H's and —OH's 

 attached to the carbon ring. 



(3) Finally, consider a pivotal carbon atom, with its attached 



H 



atoms or groups, say H — C — H. 



H 



In 3-dimensional space the carbon atom is situated in the centre 



of a tetrahedron, / Jl\ and the attached atoms, or groups, 



are placed at the solid angles of the tetrahedron. If there are, 

 say, four different attached groups, i, 2, 3, 4, then we might 

 see these (when we look at one face of the tetrahedron) thus 



