¹³C NMR Spectroscopy of Substituted Cyclohexanes

Abstract

Lead Germanate thin films have been successfully deposited on different electrodes by a metalorganic chemical vapor deposition (MOCVD) system for the first time. Three different phases have been characterized. The single c-axis oriented Pb 5 Ge 3 O 11 phase has been deposited on Ir, Ir/Pt (Pt on top) and Pt electrodes respectively and shows a very uniform surface. A lead rich phase, Pb 3 GeO 5 , also was formed with a polycrystalline structure and large grain size exhibiting a very rough surface. Finally an unknown oxygen and/or lead deficient phase, which is considered here a non-stoichiometric phase of Pb 5 Ge 3 O 11 , appeared with a smaller interplanar spacing of about 9.4 Å compared with 10.68 Å for the Pb 5 Ge 3 O 11 phase. This unknown phase can co-exist with the c-axis oriented Pb 5 Ge 3 O 11 phase and deteriorates its ferroelectric properties. Post deposition annealing in an oxygen or oxygen plus lead ambient can recover the ferroelectric properties of this film.

Design of Mechanically Robust High-Tg Polymers: Synthesis and Dynamic Mechanical Relaxation Behavior of Glassy Poly(ester carbonate)s with Cyclohexylene Rings in the Backbone

“…Cyclohexane undergoes ring inversion in either the gaseous or the liquid state. The various kinetic parameters for the chair−chair interconversion, such as activation energy (Δ E *), enthalpy of activation (Δ H *), entropy of activation (Δ S *), and preexponential factor f 0 , have been established by various techniques, such as NMR, , IR, and molecular simulation. , Generally, the equation expressing the rate of inversion is f = f 0 e -Δ E */ RT , where the activation energy is 11 kcal/mol and the preexponential factor f 0 is 2 × 10 13 Hz. So at room temperature, in both the solution and the gaseous states, cyclohexane rings undergo inversion at a rate of close to megahertz.…”

Hindered Internal Rotation about a C-N Bond in Some Trisubstituted 1,3,5-Triazines

“…In order to study this question, we recorded the 1 H NMR spectra of trisubstituted triazines 1-3 in the temperature range 20-90°C. 1a-i 2a-h 3a-e 1 a R 1 = R 2 = NMe 2 , R 3 = Cl; b R 1 = NMe 2 , R 2 = OMe, R 3 = Cl; c R 1 = NHMe, R 2 = OMe, R 3 = Cl; d R 1 = R 2 = NHEt, R 3 = CN; e R 1 = R 2 = NHCHMe 2 , R 3 = CN; f R 1 = NHEt, R 2 = NHCMe 3 , R 3 = Cl; g R 1 = NMe 2 , R 2 = OMe, R 3 = OC 6 H 4 COOEt-p; h R 1 = NHEt, R 2 = SMe, R 3 = OC 6 H 4 COOEt-p; i R 1 = R 2 = NHCHMe 2 , R 3 = OC 6 H 4 COOMe-p; 2 a R 1 = R 2 = NMe 2 , R 3 = OH; b R 1 = NMe 2 , R 2 = OMe, R 3 = OH; c R 1 = NHEt, R 2 = OMe, R 3 = OH; d R 1 = NHEt, R 2 = OMe, R 3 = OCHMe 2 ; e R 1 = R 2 = NHEt, R 3 = OH; f R 1 = R 2 = NHEt, R 3 = OEt; g R 1 = R 2 = NHCHMe 2 , R 3 = OH; h R 1 = R 2 = NHCHMe 2 , R 3 = OMe; 3 a R 1 = R 2 = NMe 2 ; b R 1 = NMe 2 , R 2 = OMe; c R 1 = NHEt, R 2 = OMe; d R 1 = R 2 = NHEt; e R 1 = R 2 = NHCHMe 2 ; a-e R 3 In the spectrum of compound 1a taken at 20°C, in the 3.0-3.2 ppm region there are two singlet signals of equal intensity (∆ν = 6.3 Hz) from the NMe 2 groups (R 1 and R 2 ). When we raised the temperature at which we recorded the spectra, they coalesced into one signal (coalescence temperature 40°C), narrowing upon further increase in temperature.…”

“…We calculated the free energy of activation (∆G*) from the Eyring equation, and we determined the exchange rate constant from the coalescence temperature and the difference between the chemical shifts of the signals in the low-temperature spectra [3] ( Table 1).…”

From molecular insights and chemical technologies to communications and expert systems: A few short thermodynamic stories

“…isomerization enthalpies of 2-and 3-methylcyclohexanols can be interpreted from the point of view of conformation analysis exactly in the same way as was done by Pitzer and co-workers for dimethylcyclohexanes [16]. It was noted [17] that for 4-methylcyclohexanol there is a stabilization of the a CH 3 a OH form. This is a possible reason for the lower isomerization enthalpy compared with 2-methylcyclohexanol as seen from our experimental results.…”