Benzoic acid, molecular orientation

Figure 10.5. Adsorbate molecular orientation at the electrode surface d) nicotinic acid (Z ) benzoic acid (c) 2,6-pyridinedicarboxylic acid. (From Ref. 12, with permission from the American Chemical Society.)...

Fig. 5. Surface diffusion of the rigid rodlike molecule 4-trans-2-(pyrid-4-yl-vinyl) benzoic acid on Pd(110). In (a) and (b) two consecutive STM images taken at 361 K are shown which demonstrate the 1-dim motion. Arrows indicate molecules whose position changed circles mark fractionally imaged molecules moving under the STM tip in the course of the measurement, (c) Model for the flat adsorption geometry explaining the two observed molecular orientations in the STM data. The length of the molecule is 12.5 A. (d) Arrhenius plot of single molecule hopping rates [75].

H-bonds with the bulk H2O determine the orientations of o-, m-, and p-amino-benzoic acids as they approach host 1 the hydrophobic end of guests o-, m-, and p-aminobenzoic acids must enter 1 more favorably. Therefore, guests with the most exposed hydrophobic portions, such as Ar3, should have the largest CICS values, as was observed. Molecular modeling studies confirm that the distances between the amino H atom and carboxylate O atom for 0-, m-, andp-aminobenzoic acids are 1.85 A, 4.98 A, and 6.87 A, respectively. With the increasing distances between these the two hydrophilic functional groups, from 0-, m-, to p-amino-benzoic acids the steric hindrance also dramatically increases and, at the same time, the exposed hydrophobic portions decrease. 

The fiber is then heat treated under tension or stretching, to perfect the crystallization and orientation of crystals of an extended molecular chain. In this way, a high-strength, high-modulus fiber is obtained. Figure 3 shows the fibril structure of a whole aromatic polyester fiber. The molecular structure is shown in Figure 3. It consists of naphthalic acid, two(2)-methyl-para-quinone and para-benzoic acid. The high orientation of the crystals, especially those of the core, is deduced from the fibrillar structure observed. 

---