Solid molecular packing

Gels made in this way have virtually no usable porosity and are called Jordi solid bead packings. They can be used in the production of low surface area reverse phase packings for fast protein analysis and in the manufacture of hydrodynamic volume columns as well as solid supports for solid-phase syntheses reactions. An example of a hydrodynamic volume column separation is shown in Fig. 13.2 and its calibration plot is shown in Fig. 13.3. The major advantage of this type of column is its ability to resolve very high molecular weight polymer samples successfully. 

Molecular Packing and Ring Interconversion by Solid State and Solntion State... 

The purpose of this article is to discuss conformational shift variations in some selected solid state spectra on the basis of discrete rotational isomeric states and to compare them with molecular packing effects. 

Figure 8.26 Schematic formula (a) molecular single crystal X-ray diffraction structure (b), and solid state packing (c) ofthe cationic gold complex [Au bimy(Ci6H33) 2]Br H20. (Reproduced from Ref [52] by permission.)...

The compounds [Au3Ira(MeN=COMe)3] ( = 2, 4, 6) obtained by stepwise addition of iodine to the cyclic tetranuclear gold(I) complexes [Au3(MeN=COMe)3] have been revisited. The structure of [Au3I6(MeN=COMe)3] (338) consists of columns of the molecular units united by weak iodine- iodine interactions which range in length from 3.636(2) A to 3.716(2) A. The solid-state molecular packing of the di-iodo and tetra-iodo complexes reveal no unusual features.1971... 

A piperidene-based intermediate was found to crystallize as either an anhydrate or a hydrate, but the impurity profile of the crystallized solids differed substantially [26], Considerations of molecular packing led to the deduction that there was more void volume in the anhydrate crystal structure than in that of the hydrate form, thereby facilitating more clathration in the anhydrate than in the hydrate phase. This phenomenon was led to a decision to crystallize the hydrate form, since lower levels of the undesired impurity could be occluded and greater compound purity could be achieved in the crystallization step. 

The true density of a solid is the average mass per unit volume, exclusive of all voids that are not a fundamental part of the molecular packing arrangement [55]. This density parameter is normally measured by helium pycnometiy, where the volume occupied by a known mass of powder is determined by measuring the volume of gas displaced by the powder. The true density of a solid is an intrinsic property characteristic of the analyte, and it is determined by the composition of the unit cell. 

Structural polymorphism has been already reported as a peculiar solid-solid phase transition with a large spectral shift in the cast film of CgAzoCioN+ Br (chapter 4). The type 1 spectrum was thermally transformed to the type VI spectrum and then backed to the type I by the isothermal moisture treatment. The reversible spectral change between the type I and VI is a good experimental evidence of Okuyama s prediction on the molecular packing. Since the type VI state is assumed to be a metastable state, the isothermal phase transition to the type I state is expected to be induced by some external stimuli. Water molecules adsorbed to cast bilayer films might act as an accelerator of the phase transition. 

At the end of the process, one obtains a large amount of information regarding the solid-state structure of a compound. Its three-dimensional structure and molecular conformation become known, as do the patterns of molecular packings that enable the assembly of the crystal. In addition, one obtains complete summaries of bond angles and bond lengths for the molecules in the crystal as well as detailed atomic coordinates for all of the atoms present in the solid. One generally finds... 

Fig. 17 Schematic diagram showing the molecular packing and topochemical polymerization of diacetylenes [30] in crystals. There are two idealized packing arrangements either (a), (b) or (c), (d) in crystals and each has two modes of polymerization. The polymerization in the solid state is said to occur smoothly when, v = 240 400 pm and y = 45° (Baughman, 1974 Baughman and Yee, 1978).

Solid-state photoreaction pathways are dependent on the structiue of 1,3-diene compounds as the reactant (i.e., molecular packing in the crystals) cyclodimer, 1,4-polymer, or EE isomer is produced depending on the structiue of the substituent X and the molecular packing in the crystals, as shown in Scheme 1 and Table 1. Here, the stereochemical structure of the products is highly regulated during the photoreactions in the crystalhne state. 

In the absence of defects, the reactivity of organic solids is mainly determined by molecular packing. Reactions in which the crystal structure holds sway over intrinsic molecular reactivity are said to be topochemically controlled (Thomas, 1974). A classic example of a topochemically controlled organic reaction in the solid state is the photodimerization of rrans-cinnamic acids studied by Schmidt et al. (see Ginsburg,... 

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