What is the compound which has empirical formula of C2H6O?

All of the butanediones have this empirical formula, and there may be other compounds also.

This answer was wrong:

Butadione: first of all: there is only one possible butadion: CH3-C(=O)-C(=O)-CH3 (also named diacetyl)

and secondly butadion is with 6 H atoms (C4H6O2). An alkanon being --C(=O)--, double bonded =O to one 'middle' C atom!.

Right SIX answers or possibilities are (plus 3 enantiomers):

• 2-hydroxybutanal and 3-hydroxybutanal (actually both have enantiomers: R- and S-forms on C'HOH)

  HC(=O)-C'HOH-CH2-CH3 and

  HC(=O)-CH2-C'HOH-CH3

• 1-hydroxybuton and 3-(R- or S-)hydroxybutanon and 4-hydroxybuton

  CH2OH-C(=O)-CH2-CH3 and

  CH3-C(=O)-C'HOH-CH3 and

  CH3-C(=O)-CH2-CH2OH

• Butanoic acid

  CH3-CH2-CH2-COOH

Improved answer: There are more possibilities:

Esters: Ethyl acetate, methyl propionate, propyl formate and isopropyl formate

Another acid: 2-methylpropanoic acid

Enediols: 3,4-dihydroxy-1-butene (R and S), 1,4-dihydroxy-2-butene (E and Z)

Ether carbonyl compounds: 3-methoxypropanal, 2-methoxypropanal, 2-ethoxyethanal, methoxypropanone

More hydroxy aldehydes: 2-hydroxy-2-methylpropanal, 3-hydroxy-2-methylpropanal

Cyclic compounds: Dioxane, 1,3-dioxacyclohexane, 2-methyl-1,3-dioxacyclopentane, 4-methyl-1,3-dioxacyclopentane (R and S) (and a series of dimethyl-1,3-dioxacyclobutanes if they are viable). There are also cyclic diols such as cyclobutane-1,2-diol (RR, SS and meso) and other cyclobutane isomers, and methylcyclopropanediol isomers. Then there are cyclic and non-cyclic peroxides with O-O bonds.

In short, there are many molecules with the formula: C4H8O2