Bond lengths of furan and furfural (Å).

Structure	Bond	Length	Ref. 13 and 30	Relative error (%)
Furan	C1–C2	1.369	1.356	0.96
	C2–C3	1.439	1.440	0.07
	C3–C4	1.369	1.356	0.96
	C4–O5	1.378	1.378	0.00
	O5–C1	1.378	1.378	0.00
Furfural	C1–C2	1.377	1.374	0.22
	C2–C3	1.426	1.419	0.49
	C3–C4	1.383	1.380	0.22
	C4–O5	1.392	1.386	0.43
	O5–C1	1.365	1.357	0.59
	C4–C6	1.460	1.451	0.62
	C6–O7	1.231	1.231	0.00