196
7 Molecular Structures from Gas-Phase Electron Diffraction
Table 7.4 Structural parameters of thymine (bond lengths r in pm and angles ∠ in degrees; see
Fig. 7.13 for atom numbering)
Parameter
r se
e (ED) a,b
r se
e (MW) b,c
r BO
e
c
r a
a
r s
d
r(N1–C2)
137.7(3)
137.82(10)
137.76
139.0(3)
134(5)
r(C2–N3)
137.8(3) 1
137.97(9)
137.83
138.8(3)
142(2)
r(N3–C4)
139.5(3) 1
139.32(10)
139.34
140.7(3)
138.4(4)
r(N1–C6)
137.2(3) 1
137.09(20) e
137.89
138.4(3)
135.5(7)
r(C4–C5)
146.6(9) e
146.35(9)
146.21
147.5(9)
145.7(4)
r(C5=C6)
134.4(16)
134.57(10)
134.55
135.1(16)
137.0(7)
r(C5–Cm)
148.7(8)
149.31(8)
149.33
149.8(8)
150.1(2)
r(C2=O2)
121.0(1) 2
120.96(10)
121.03
121.3(1)
r(C4 = O4)
121.5(1) 2
121.54(10)
121.45
121.8(1)
r(N1–H1)
100.8(9) 3
100.39(8)
100.41
102.3(9)
99.8(2)
r(N3–H3)
101.2(9) 3
100.87(7)
100.85
102.8(9)
100.7(3)
r(C6–H)
109.4(11) 4
108.04(12)
108.02
111.0(11)
r(Cm–Hs)
110.1(11) 4
108.83(12)
108.82
111.6(11)
r(Cm–Ha)
110.2(11) 4
108.93(11)
108.90
111.8(11)
∠(N3C2N1)
112.8(5)
112.77(7)
112.73
113.7(8)
∠(C4N3C2)
128.0(5)
127.96(6)
128.08
126(2)
∠(C5C4N3)
114.8(5)
114.81(6)
114.97
115.5(3)
∠(C6C5C4)
117.6(6) e
117.88(7)
117.78
117.3(4)
∠(O2C2N1)
123.1(9)
123.39(9)
123.46
∠(O4C4N3)
120.6(12)
120.42(9)
120.44
∠(H3N3C2)
114.8(15) e
115.52(9)
115.64
117(2)
∠(C2N1H1)
114.8(11)
115.24(8)
115.32
∠(CmC5C4)
118.0(9)
117.84(7)
118.07
∠(HaCmC5)
109.5(15) 5
110.56(11)
110.57
∠(HsCmC5)
110.0(15) 5
110.77(12)
110.78
Reprinted from Journal of Molecular Structure, 1076. Vogt N, Demaison J, Ksenafontov DN,
Rudolph HD. A benchmark study of molecular structure by experimental and theoretical methods:
Equilibrium structure of thymine from microwave rotational constants and coupled-cluster
computations, 483–489. Copyright 2014, with permission from Elsevier
a Parenthesized uncertainties are 3σ values in units of the last significant digits; parameters with
equal superscripts were refined in one group (Vogt et al. 2008)
b The spectroscopic r se
e (MW) and electron diffraction r se
e (ED) structures are derived using the
MP2_ae/6-311G(d,p) anharmonic (cubic) force field
c Vogt et al. (2014); the r BO
e
structure of CCSD(T)_ae/wCVQZ quality was estimated as r BO
e
=
r e (CCSD(T)_ae/wCVTZ + [r e (MP2_ae/wCVQZ − r e (MP2_ae/wCVTZ], for significance of this
structure, see Sects. 2.10 and 2.11
d López et al. (2007)
e Dependent parameter
7 Molecular Structures from Gas-Phase Electron Diffraction
Table 7.4 Structural parameters of thymine (bond lengths r in pm and angles ∠ in degrees; see
Fig. 7.13 for atom numbering)
Parameter
r se
e (ED) a,b
r se
e (MW) b,c
r BO
e
c
r a
a
r s
d
r(N1–C2)
137.7(3)
137.82(10)
137.76
139.0(3)
134(5)
r(C2–N3)
137.8(3) 1
137.97(9)
137.83
138.8(3)
142(2)
r(N3–C4)
139.5(3) 1
139.32(10)
139.34
140.7(3)
138.4(4)
r(N1–C6)
137.2(3) 1
137.09(20) e
137.89
138.4(3)
135.5(7)
r(C4–C5)
146.6(9) e
146.35(9)
146.21
147.5(9)
145.7(4)
r(C5=C6)
134.4(16)
134.57(10)
134.55
135.1(16)
137.0(7)
r(C5–Cm)
148.7(8)
149.31(8)
149.33
149.8(8)
150.1(2)
r(C2=O2)
121.0(1) 2
120.96(10)
121.03
121.3(1)
r(C4 = O4)
121.5(1) 2
121.54(10)
121.45
121.8(1)
r(N1–H1)
100.8(9) 3
100.39(8)
100.41
102.3(9)
99.8(2)
r(N3–H3)
101.2(9) 3
100.87(7)
100.85
102.8(9)
100.7(3)
r(C6–H)
109.4(11) 4
108.04(12)
108.02
111.0(11)
r(Cm–Hs)
110.1(11) 4
108.83(12)
108.82
111.6(11)
r(Cm–Ha)
110.2(11) 4
108.93(11)
108.90
111.8(11)
∠(N3C2N1)
112.8(5)
112.77(7)
112.73
113.7(8)
∠(C4N3C2)
128.0(5)
127.96(6)
128.08
126(2)
∠(C5C4N3)
114.8(5)
114.81(6)
114.97
115.5(3)
∠(C6C5C4)
117.6(6) e
117.88(7)
117.78
117.3(4)
∠(O2C2N1)
123.1(9)
123.39(9)
123.46
∠(O4C4N3)
120.6(12)
120.42(9)
120.44
∠(H3N3C2)
114.8(15) e
115.52(9)
115.64
117(2)
∠(C2N1H1)
114.8(11)
115.24(8)
115.32
∠(CmC5C4)
118.0(9)
117.84(7)
118.07
∠(HaCmC5)
109.5(15) 5
110.56(11)
110.57
∠(HsCmC5)
110.0(15) 5
110.77(12)
110.78
Reprinted from Journal of Molecular Structure, 1076. Vogt N, Demaison J, Ksenafontov DN,
Rudolph HD. A benchmark study of molecular structure by experimental and theoretical methods:
Equilibrium structure of thymine from microwave rotational constants and coupled-cluster
computations, 483–489. Copyright 2014, with permission from Elsevier
a Parenthesized uncertainties are 3σ values in units of the last significant digits; parameters with
equal superscripts were refined in one group (Vogt et al. 2008)
b The spectroscopic r se
e (MW) and electron diffraction r se
e (ED) structures are derived using the
MP2_ae/6-311G(d,p) anharmonic (cubic) force field
c Vogt et al. (2014); the r BO
e
structure of CCSD(T)_ae/wCVQZ quality was estimated as r BO
e
=
r e (CCSD(T)_ae/wCVTZ + [r e (MP2_ae/wCVQZ − r e (MP2_ae/wCVTZ], for significance of this
structure, see Sects. 2.10 and 2.11
d López et al. (2007)
e Dependent parameter