1616
F. Ros and I. Barbero
(E)-2-Methyl-3-(20-methylphenyl)-4-nitro-3-buten-2-ol (2d, C12H15NO3)
Reaction time 72h; purification by column chromatography (silica gel, petroleum-ether=AcOEt 9=1);
1
yield 28%; mp 49–50ꢃC; H NMR (CDCl3, 300 MHz): ꢀ ¼ 1.39 (s, 3H, C(CH3)CH3), 1.52 (s, 3H,
C(CH3)CH3), 1.75 (s, 1H), 2.26 (s, 3H), 7.00 (d, J ¼ 7.5 Hz, 1H), 7.25 (m, 3H), 7.51 (s, 1H) ppm; 13
C
NMR (CDCl3, 50MHz): ꢀ ¼ 20.2, 28.9 (C(CH3)CH3), 29.4 (C(CH3)CH3), 73.6, 125.4, 127.0, 128.4,
130.4, 133.1, 136.0, 136.4, 156.1 ppm.
(E)-3-(40-Fluorophenyl)-2-methyl-4-nitro-3-buten-2-ol (2e, C11H12FNO3)
Reaction time 48 h; purification by recrystallisation (petroleum-ether=CH2Cl2); yield 57%; mp
1
86–87ꢃC; H NMR (CDCl3, 300 MHz): ꢀ ¼ 1.42 (s, 6H), 1.72 (s, 1H), 7.10 (d, J ¼ 1.0 Hz, 2H),
7.12 (s, 2H), 7.49 (s, 1H) ppm.
(E)-2-Methyl-4-nitro-3-(40-nitrophenyl)-3-buten-2-ol (2f, C11H12N2O5)
Reaction time 22 h; purification by recrystallisation (petroleum-ether=CH2Cl2); yield 59%; mp
1
143–146ꢃC; H NMR ((CD3)2SO, 300 MHz): ꢀ ¼ 1.26 (s, 6H), 5.66 (s, 1H), 7.49 (d, J ¼ 8.8 Hz,
2H), 7.54 (s, 1H), 8.25 (d, J ¼ 8.8 Hz, 2H) ppm.
(E)-, (Z)-2-Methyl-3-(40-methylphenyl)-4-nitro-3-penten-2-ols (3a, 3b, C13H17NO3)
The geometrical isomers were obtained from reaction of 1b with EtNO2 working similarly to the
procedure for 2a–2f; reaction time 72 h; the isomers were separated from each other by TLC (silica
gel, petroleum-ether=AcOEt 9=1, Et2O as eluent, 3a at higher Rf).
1
Isomer 3a: yield 7%; mp 114–123ꢃC; H NMR (CDCl3, 500MHz): ꢀ ¼ 1.36 (s, 6H, CMe2), 1.83
(s, 3H, C¼CMe), 1.86 (s, 1H, OH), 2.37 (s, 3H, 40-Me), 7.04 (d, J ¼ 7.9 Hz, 2H, 20-, 60-H), 7.20 (d,
J ¼ 7.9 Hz, 2H, 30-, 50-H) ppm; 13C NMR (CDCl3, 125 MHz): ꢀ ¼ 19.4, 21.2, 29.5, 73.7, 128.3, 129.3,
133.6, 137.9, 140.7, 144.2 ppm.
Isomer 3b: yield 11%; mp 97–100ꢃC; 1H NMR (CDCl3, 500MHz): ꢀ ¼ 1.37 (s, 6H), 1.61 (s, 1H),
2.31 (s, 3H), 2.54 (s, 3H, C¼CMe, NOE by 20-, 60-H), 6.98 (d, J ¼ 7.9 Hz, 2H, 20-, 60-H), 7.10 (d,
J ¼ 7.9 Hz, 2H) ppm; 13C NMR (CDCl3, 50 MHz): ꢀ ¼ 17.5, 21.2, 30.3, 73.0, 128.4, 128.8, 133.0,
137.8, 141.7, 149.4ppm.
Methods of Calculation
For the ꢁrGꢃ values in the gas phase (Table 2) the enthalpies of formation and the entropies of MeNO2
and HCl were available and those of the other compounds were obtained by summation of Benson
contributions of atomic groups [8]; involved symmetry numbers: n ¼ 18 (1a), 36 (4, 5, 2a). The
enthalpic contribution (ꢀfHꢃ) for O2NCH¼ was found out subtracting the contribution of H2C¼ from
an approximate enthalpy of formation of H2C¼CHNO2 (54 kJmolꢅ1, obtained from the enthalpies of
ꢂ
formation of H2C¼CH and NO2, and the enthalpy of dissociation for the C–NO2 bond in
H2C¼CMeNO2 [17], this increased by 8 kJ molꢅ1 to offset the substitution of Me for H):
ꢀfHꢃ ¼ 28kJ molꢅ1 (O2NCH¼). Steric corrections: ꢀfHꢃ ¼ 2.5 (5, cis interact.), 4.2 (2a, stagg. con-
form.), 6.7 (4, stagg. conform.) kJmolꢅ1; ꢀSꢃ ¼ 6.7 J Kꢅ1 molꢅ1 (5, cis interact.). The entropy of
mixing of enantiomers (Rln2) was included for 4 and 5.
For the estimation of pv values (Table 3) by pv-T correlation the following normal boiling points
were estimated with Meissner’s equation [9]: bp¼ 176 (Me2SO ꢂ HCl, treated as an ordinary covalent
compound), 310 (5), 335 (2a), 343ꢃC (4).
For the potential energy of hydrogen bonding (ꢀrUpot) for Me2SOꢂ HCl (concerning the ꢁrHꢃ value
in Scheme 5) a literature value for H3POꢂ HCl was adopted (ꢅ27.7kJ molꢅ1) [18]. The vibrational
energy of bonding (ꢀrUvibꢃ) was attributed entirely to the five vibrational degrees of freedom rised by
bonding, to each of which a frequency of 6ꢆ1012 Hz was assigned (representing ca. 2=5 ꢃof the zero-
0
point vibrational energy of hydrogen bonding for H3POꢂ HCl, "vib ¼ hꢄ=2); the ꢀrUvib value was
obtained from this frequency together with the formula of statistical thermodynamics for the energy of