Steric parameters of selected atoms and functional groups.

Atom or group	−ΔG (kcal mol−1)	−Es	ν	I X–H (kJ mol−1)	wSterimol
					wB1 (Å)	wL (Å)	wB5 (Å)
H	—	0.00	0.00	∼4.0	—	—	—
F	0.15	0.46	0.27	19.2	1.52	3.12	2.03
Cl	0.43	0.97	0.55	38.1	1.80	3.99	2.03
Br	0.38	1.16	0.65	42.5	1.95	4.29	2.03
CN	0.17	0.51	—	25.6	—	—	—
NO2	1.10	1.01/2.52a	—	32.4	—	—	—
Me	1.70	1.24	0.52	40.4	1.88	3.43	2.02
CH2F	1.59	1.48	0.62	—	—	—	—
CHF2	1.85	1.91	0.68	—	—	—	—
CF3	2.10	2.40	0.91	50.6	1.87	3.75	2.60
i Pr	2.15	1.71	0.76	52.6	1.91	4.56	3.17
SiMe3	2.50	3.36	1.40	47.2	—	—	—
Ph	3.00	1.01/3.82a	1.66	33.1	1.70	6.80	3.15
t Bu	∼4.20	2.78	1.24	76.6	2.76	4.54	3.17

^aThickness/width values.