The catalytic synthesis of 1,3-diaminopropane from 1,3-propanediol and ammonia was studied in a continuous fixed-bed reactor in the pressure range 50 to 150 bar. The unsupported Co-based catalysts applied were characterized by N₂physisorption, XRD, XPS, TPR, and ammonia adsorption using pulse thermal analysis and DRIFT spectroscopy. The latter investigations revealed that the best catalyst, 95 wt% Co–5 wt% Fe, contained only very weak acidic sites, unable to chemisorb ammonia. The absence of strong acidic and basic sites was crucial to suppress the various acid/base-catalyzed side reactions (retro-aldol reaction, hydrogenolysis, alkylation, disproportionation, dimerization, oligomerization). Other important requirements for improved diaminopropane formation were the use of excess ammonia (molar ratio NH₃/diol>20) and the presence of the metastable β-Co phase. A small amount of Fe additive could efficiently hinder the transformation of this phase into the thermodynamically stable α-Co phase and thus prevent catalyst deactivation up to 10 days on stream. Application of supercritical ammonia almost doubled the selectivity to amino alcohol and diamine. The selectivity enhancement in the near-critical region is attributed to elimination of the interphase mass transport limitations and to the resulting higher surface ammonia concentration.

Extensive ab initio calculations of the phenolâ‹…H₂O complex were performed at the Hartree–Fock level, using the 6â€�31G(d,p) and 6â€�311++G(d,p) basis sets. Fully energyâ€�minimized geometries were obtained for (a) the equilibrium structure, which has a translinear H bond and the H₂O plane orthogonal to the phenol plane, similar to (H₂O)₂; (b) the lowestâ€�energy transition state structure, which is nonplanar (C₁ symmetry) and has the H₂O moiety rotated by ±90°. The calculated MP2/6â€�311G++(d,p) binding energy including basis set superposition error corrections is 6.08 kcal/mol; the barrier for internal rotation around the H bond is only 0.4 kcal/mol. Intraâ€� and intermolecular harmonic vibrational frequencies were calculated for a number of different isotopomers of phenolâ‹…H₂O. Anharmonic intermolecular vibrational frequencies were computed for several intermolecular vibrations; anharmonic corrections are very large for the β₂ intermolecular wag. Furthermore, the H₂O torsion Ï„ around the Hâ€�bond axis, and the β₂ mode are strongly anharmonically coupled, and a twoâ€�dimensional Ï„/β₂ potential energy surface was explored. The role of tunneling splitting due to the torsional mode is discussed and tunnel splittings are estimated for the calculated range of barriers. The theoretical studies were complemented by a detailed spectroscopic study of hâ€�phenolâ‹…H₂O and dâ€�phenolâ‹…D₂O employing twoâ€�color resonanceâ€�twoâ€�photon ionization and dispersed fluorescence emission techniques, which extends earlier spectroscopic studies of this system. The β₁ and β₂ wags of both isotopomers in the S₀ and S₁ electronic states are newly assigned, as well as several other weaker transitions. Tunneling splittings due to the torsional mode may be important in the S₀ state in conjunction with the excitation of the intermolecular σ and β₂ modes.

A combined experimental and theoretical study of the 2â€�naphtholâ‹…H₂O/D₂O system was performed. Two different rotamers of 2â€�naphthol (2â€�hydroxynaphthalene, 2HN) exist with the O–H bond in cisâ€� and transâ€�position relative to the naphthalene frame. Using Hartree–Fock (HF) calculations with the 6â€�31G(d,p) basis set, fully energyâ€�minimized geometries were computed for both cisâ€� and transâ€�2HNâ‹…H₂O of (a) the equilibrium structures with transâ€�linear Hâ€�bond arrangement and C_s symmetry and (b) the lowestâ€�energy transition states for H atom exchange on the H₂O subunit, which have a nonplanar C₁ symmetry. Both equilibrium and transition state structures are similar to the corresponding phenolâ‹…H₂O geometries. The Hâ€�bond stabilization energies with zero point energy corrections included are ≊5.7 kcal/mol for both rotamers, ≊2.3 kcal/mol stronger than for the water dimer, and correspond closely to the binding energy calculated for phenolâ‹…H₂O at the same level of theory. Extension of the aromatic Ï€â€�system therefore hardly affects the Hâ€�bonding conditions. The barrier height to internal rotation around the Hâ€�bond only amounts to 0.5 kcal/mol. Harmonic vibrational analysis was carried out at these stationary points on the HF/6â€�31G(d,p) potential energy surface with focus on the six intermolecular modes. The potential energy distributions and Mâ€�matrices reflect considerable mode scrambling for the deuterated isotopomers. For the a′ intermolecular modes anharmonic corrections to the harmonic frequencies were evaluated. The β₂ wag mode shows the largest anharmonic contributions. For the torsional mode Ï„ (H₂O Hâ€�atom exchange coordinate) the vibrational level structure in an appropriate periodic potential was calculated. On the experimental side resonantâ€�twoâ€�photon ionization and dispersed fluorescence emission spectra of 2HNâ‹…H₂O and dâ€�2HNâ‹…D₂O were measured. A detailed assignment of the bands in the intermolecular frequency range is given, based on the calculations. The predicted and measured vibrational frequencies are compared and differences discussed.