Benzoic acid crystallization

Fig. 40. Flole-burning spectra of thioindigo in benzoic acid crystal at 1.35 K. The scanning laser frequency cu is measured with respect to the burning laser frequency cUb is detuning of the burning laser frequency relative to the center of absorption line.

In 20 liters of human urine is dissolved 1,200 grams of sodium benzoate (6% weight by volume). The solution is acidified with aqueous hydrochloric acid (assay about 7.5% HCI) to a pH of 4.5 resulting in a heavy precipitation. This requires 10% of the original urine volume, or about 2 liters of aqueous hydrochloric acid. The suspension is stirred 20 minutes and is then allowed to stand for about 30 minutes. The mixture so obtained is filtered on a Buchner funnel that has been prepared with a precoat of benzoic acid crystals over filter paper. The filter cake is washed with a saturated benzoic acid solution, then sucked dry. The benzoic acid cake with the adsorbed urokinase weighs 2,060 grams. 

Skinner, J. L. and Trommsdorf, H. P. Proton transfer in benzoic acid crystals A chemical spin-boson problem. Theoretical analysis of nuclear magnetic resonance, neutron scattering, and optical experiments, J.Chem.Phys., 89 (1988), 897-907... 

Dick [1977] explained this behavior within the framework of a phonon-assisted tunneling mechanisms using the TLS approximation and golden rule formalism (see Sections 2.3 and 6.4). One-phonon transitions dominate the mechanism at low temperatures, resulting in a linear dependence of k with 7 this follows directly from relation (6.27) when j3/Wl. At higher temperatures, the main contribution comes from Raman processes, leading to a T4 dependence of the rate constant. This predicted T4 temperature dependence for RbBr OH- is analogous to results obtained by Silbey and Trommsdorf [1990] for two-proton transfer in benzoic acid crystals (see Section 6.4). 

Curtin et. al. W exposed benzoic acid crystals to ammonia gas and generated ammonium benzoate. As shown In Figure 7, the (101) faces of the crystals become opaque while the (001) faces remain clear. The resistance of molecules at the (001) faces to reaction with ammonia Is explainable by the relatively unexposed carboxyl groups within this region. 

Commercial benzaldehyde inhibited against autoxidation with 0.1% hydroquinone is usually satisfactory. If the material available is yellow or contains benzoic acid crystals it should be shaken with equal volumes of 5% sodium carbonate solution until carbon dioxide is no longer evolved and the upper layer dried over calcium chloride and distilled (bp 178-180°C), with avoidance of exposure of the hot liquid to air. The distillation step can be omitted if the benzaldehyde is colorless. 

It is heavier than water, in which it sinks as an oil, and by which it is soon converted into benzoic and hydrocyanic acids. If a drop be suffered to spread upon water, it will be found completely changed in a day into a radiating mass of benzoic acid crystals. By boiling with water, it is rapidly decomposed into the benzoic and prussic acids. It is readily inflammable, burning with a white, but very smoky flame. 

The availability of the coherent proton tunneling and cooperative proton tunneling and transfer of four protons in hydrogen bonds of benzoic acids crystals (including dye doped) have been revealed by Trommsdorff and collaborators [12,13] by reading the electron spectra of the crystals. 

Dihydroxy benzoic acid crystallizes in two polymorphic forms monoclinic and orthorhombic. The molecule in the monoclinic form adopts the syn-anti conformation (20) while it adopts the syn-syn conformation in the orthorhombic form (21). 

F. Fillaux, M.H. Limage F. Remain (2002). Chem. Phys., 276, 181-210. Quantum proton transfer and interconversion in the benzoic acid crystal vibrational spectra, mechanism and theory. 

M.R. Johnson H.P Trommsdorff (2002). Chem. Phys. Lett., 364, 34-38. Dispersion of vibrational modes in benzoic acid crystals. 

Here A is the energy asymmetry of the potential energy minima and J is the tunneling splitting of the ground vibrational state (in the considered doublewell potential when A equals zero). In benzoic acid crystals A A , because J 0.2 cm-i [58] and AE 65 [48]. 

This approach is able to model a variety of condensed phase chemical reactions with essentially experimental accuracy [16]. We did And, however, one specific experimental system for which this methodology was not able to reproduce experimental results, and that is proton transfer in benzoic acid crystals. In developing a physical understanding of this system, we first identified the concept of the promoting vibration. 

Table 9.1. Activation energies for H and D transfer in benzoic acid crystals at T = 300 K. Three values are shown the activation energies calculated using a one- and two-dimensional Kramers problem and the experimental values.

The low level of primary kinetic isotope effect in the benzoic acid crystal when... 

Toyokura, K. et al. (1976a) Growth of naphthalene from molten naphthalene-benzoic acid crystallized on a cooled cylindrical surface. AIChE Symposium Series No. 153, 72, 87-93. 

Schmidt, C., Yurudu, C., Wachsmuth, A., and Ulrich, J. (2011) Modeling the morpholep of benzoic acid crystals grown... 

Figure 11 SEM photographs of benzoic acid crystals obtained using (top) a capillary nozzle and (bottom) a 0.5-p.m pore size frit. (From Ref. 96.)... 

Thirdly, the collision-induced Raman resonances can expand the application of Raman spectroscopy to situations where the conventional Raman susceptibility vanishes. Andrews et al., for example, have demonstrated that sharp vibrational transitions in an initially unpopulated excited electronic state of a molecule can be observed as extra four-wave mixing resonances, even though they cannot be observed in absorption because of rapid dephasing of the electronic transition. In these experiments pentacene molecules were doped in a benzoic acid crystal, and phonon scattering rather than collisions provided the dephasing mechanism. CARS of equally-populated ground state rotational levels in molecules would also become possible by observing collision-induced resonances. 

Benzoic Acid crystals 23 28 9 saturated 23 8 Not tested plastic expected to be unaffected " crystals 52 28 9 Plastic was unaffected for duration of test In accordance with ASTM " D543-84 saturated 52 8 Not tested plastic expected to be unaffected "... 

Kryschi, C., Fleischhauer, H.C., and Wagner, B. (1992) The mechanism of singlet to triplet transitions of pentacene guests in p-terphenyl and benzoic acid crystals. Chem. Phys., 161, 485. 

Figure 5. Top, preferred orientation exhibited by a) benzoic acid crystals and b) 4-nitroaniline crystals grown from the gas phase onto (OTO)sa- Nucleation is initiated at the [10T]sa ledges. Bottom, schematic representation of the orientations of benzoic acid and 4-nitroaniline on (OTO)sa. The lattice parameters and directions for succinic acid, benzoic acid and 4-nitroaniline are also depicted. (Adapted from ref. 15.)...

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