123-42-2 2-pentanone, 4-hydroxy-4-methyl- 4-hydroxy-4-methyl-2-pentanone 4-hydroxy-4-methylpentan-2-one InChI=1/C6H12O2/c1-5(7)4-6(2,3)8/h8H,4H2,1-3H diacetone alcohol