Computational Chemistry Comparison and Benchmark DataBase Release 22 (May 2022) Standard Reference Database 101 National Institute of Standards and Technology
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Tautomer energy comparison

using model chemistry: MP2=FULL/6-311G*

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			-24	-7	allene	propyne	-17
C4H6			-38	-49	Cyclobutene	1,3-Butadiene	11
C4H6			-47	-51	1,2-Butadiene	1,3-Butadiene	4
C4H6			-13	3	1,2-Butadiene	1-Butyne	-16
C4H6			-36	-17	1,2-Butadiene	2-Butyne	-20
C4H6			-64	-82	1-Methylcyclopropene	1,2-Butadiene	19
C4H6			40	42	Methylenecyclopropane	1-Methylcyclopropene	-2
C3H6O			-125	-110	Oxetane	Propanal	-14
C4H8			-16	-33	cyclobutane	1-Butene	17
C3H4O2			22	29	2-Propenoic acid	β–Propiolactone	-7
C4H6S			-3	4	Thiophene, 2,5-dihydro-	Thiophene, 2,3-dihydro-	-8
C5H8			28	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	3
C5H8			-46	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	6