C3H4O

C₃H₄O is a chemical formula that represents each of several actual and hypothetical compounds that differ in structure, but each consist of three atoms of carbon, four of hydrogen, and one of oxygen. The following compounds are among them:

Name	CAS #	Notes	Structure
Oxetene, 2H-Oxete	287-25-2	Synthesized;[1] unstable.[2] Can be made by using light to cyclize acrolein.[3]
2-Oxabicyclo[1.1.0]butane[4]	35553-05-0
Acrolein, 2-propenal	107-02-8	Forms from pollutants, burning, metabolism.[5] Cis and trans forms; cis form predominant.[5]
Propa-1,2-dien-1-ol[6]	81788-96-7	Synthesized.[7] Tautomerizes "quantitatively" to acrolein above -50 °C.[7]
Propargyl alcohol or 2-propyn-1-ol	107-19-7	"Mild, geranium odor"[8] Used in synthesis, as corrosion inhibitor, soil fumigant.[9]
Methoxy ethyne, methoxyacetylene	6443-91-0
Prop-1-yn-1-ol,[10] 1-propynol[11]	6175-54-8
Methylketene or 1-propen-1-one[12]	6004-44-0	Synthesized.[13] Intermediate in acrolein pyrolysis.[14] Of astronomical interest.[13]
Methylene oxirane,[15] allene oxide	40079-14-9	Synthesized;[16] predicted (1968) to isomerize "readily" to cyclopropanone.[16][17][needs update]
Cyclopropanone	5009-27-8	Synthesized; unstable due to polymerization and ring-opening.[18] Derivatives used in synthesis, biology.[18] Tautomer of 1-cyclopen-1-ol[citation needed]
Cycloprop-1-en-1-ol, cyclopropene alcohol[19]	81788-95-6	Tautomer of cyclopropanone; Not synthesized[citation needed]
2-Cyclopropenol or 1-hydroxy-2-cyclopropene[dubious – discuss]	81788-94-5	Not synthesized[citation needed]
1,2-Epoxypropene or 2-methyloxirene[20]	2835-41-8	Synthesized; unstable. Product of ionized diazoacetone; isomerizes "rapidly" to methylketene, acrolein, methoxyethyne, and/or 1-propynol.[21][22]