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: B3LYP/cc-pV(T+d)Z

formula	sketch		Energy (kJ mol-1)		Name		difference
	A	B	calculated	experiment	A	B
C3H4			9	-7	allene	propyne	16
C4H6			-90	-82	1-Methylcyclopropene	1,2-Butadiene	-8
C4H6			-67	-49	Cyclobutene	1,3-Butadiene	-18
C4H6			-43	-51	1,2-Butadiene	1,3-Butadiene	8
C4H6			-8	-17	1,2-Butadiene	2-Butyne	8
C4H6			48	42	Methylenecyclopropane	1-Methylcyclopropene	7
C3H4O2			45	29	2-Propenoic acid	β–Propiolactone	16
C5H8			35	25	1,3-Pentadiene, (E)-	1,4-Pentadiene	10
C5H8			60	64	1,3-Pentadiene, (E)-	1,2-Pentadiene	-4
C5H8			-42	-52	1,2-Butadiene, 3-methyl-	1,3-Butadiene, 2-methyl-	10
C5H10			-11	-5	1-Butene, 2-methyl-	2-Butene, 2-methyl-	-6
C5H10			-35	-29	Cyclopropane, 1,1-dimethyl-	1-Butene, 2-methyl-	-6