Table 6. Second-Order Perturbation Theory Analysis of the Most Interacting NBOs of the Studied Compounds at the M06-2X/6-311++G(d,p) Level of Theory.

donor (i)	occupancy	acceptor (j)	occupancy	E(2)a [kcal/mol]	E(j)–E(i)b [au]	F(i, j)c [au]	hybrid	AO (%)
CHP
σC3–H16	1.97829	σ*C1–C2	0.01685	4.10	0.88	0.054	sp33.51	s(22.16%)p(77.80%)d(0.04%)
σC7–H21	1.98058	σ*C5–H11	0.01699	3.09	0.89	0.047	sp2.59	s(27.84%)p(71.97%)d(0.20%)
FCH
LP3(F21)	1.97535	σ*C1–C4	0.02694	3.95	0.78	0.049	sp99.99	s(0.10%)p(99.85%)d(0.05%)
σC3–H10	1.97814	σC5–H11	0.01667	3.31	0.89	0.048	sp3.53	s(22.11%)p(77.84%)d(0.04%)
σC2–H14	1.97572	σ*C1–C4	0.02694	3.35	0.88	0.049	sp3.42	s(22.61%)p(77.34%)d(0.05%)
BrCHP
σC3–H15	1.97560	σ*C1–C2	0.02326	4.34	0.87	0.055	sp3.52	s(22.11%)p(77.85%)d(0.04%)
σC4–C6	1.97371	σ*C1–Br21	0.04348	3.28	0.64	0.041	sp2.62	s(27.58%)p(72.23%)d(0.19%)
σC6–H13	1.97756	σ*C1–C4	0.02395	4.00	0.86	0.053	sp3.53	s(22.06%)p(77.90%)d(0.05%)
ClCHP
σC2–H14	1.97672	σ*C3–C5	0.01659	4.03	0.88	0.053	sp3.42	s(22.59%)p(77.36%)d(0.05%)
σC2–H9	1.97755	σ*C1–H8	0.02578	3.61	0.88	.050	sp3.47	s(22.38%)p(77.57%)d(0.05%)
Oxepane
σC6–H17	1.97481	σ*C4–O19	0.02542	4.50	0.79	0.053	sp3.48	s(22.32%)p(77.64%)d(0.04%)
σC4–H15	1.98146	σ*C2–O19	0.02544	3.12	0.81	0.045	sp3.14	s(24.12%)p(75.82%)d(0.06%)
Azepane
σC4–H16	1.97645	σC6–N19	0.01912	4.82	0.85	0.057	sp3.47	s(22.38%)p(77.57%)d(0.04%)
LP(1)N19	1.91097	σC3–C5	0.02909	7.11	0.66	0.062	sp7.15	s(12.26%)p(87.63%)d(0.10%)
Thiepane
σC1–H13	1.97863	*σC2–C3	0.01734	4.01	0.88	0.053	sp3.53	s(22.04%)p(77.91%)d(0.05%)
LP(2)S19	1.94015	σ*C3–C5	0.02631	4.75	0.61	0.049	sp99.99	s(0.47%)p(99.50%)d(0.02%)

^aE2 represents the energy of hyperconjugative interactions (stabilization energy).

^bEnergy difference between the donor and acceptor E(i) and E(j) NBO orbitals.

^cF(i, j) is the Fock matrix element between I and j NBO, and LP (n)a is a valence lone pair orbital (n) on atom (A).