Melting, crystalline solids

Because of its irregular structure, ar-PP is an amorphous polymer with a softening point lower than that of it-PP. In contrast, because of its regular structure, commercial it-PP is a higher-melting crystalline solid. It is important to note that similar stereochemical concepts apply to other vinyl polymers with pendant groups, such as polyvinyl chloride (PVC) and polystyrene (PS). 

The cis-[Pt(PR3 )2Cl2] compounds, where R = alkyl, were converted smoothly to trans-[Pt(PR3 )2HCl] by treating them with hydrazine hydrate in a mixture of ethanol and chloroform. Chloroform must be added since the complexes are insoluble in pure ethanol. The hydride complexes are cream-colored, low-melting, crystalline solids that closely resemble the physical properties of the parent dichloro complexes. 

When [Pt(COD)2] (10) is treated with 4 equiv of tertiary phosphine in a hexane solution under nitrogen, [Pt(PR3)4] is formed. These platinum(O) complexes are yellow, air-sensitive, low-melting, crystalline solids with solubility properties that are very similar to the parent phosphines. When dissolved in solution these complexes reversibly dissociate (see Equation 4). Thus the P-31 NMR spectra in benzene... 

The trans- [Rh(PR3)2Cl(CO)] complexes were prepared by treating [RhCl(CO)2]2 under nitrogen in chloroform solution with 2 equiv of tertiary phosphine per rhodium atom. The only side product was carbon monoxide so that purification by recrystallization from ethanol or ethanol-chloroform was relatively simple. The lower-molecular-weight trialkylphosphine and higher-molecular-weight triarylphos-phine complexes were orange, viscous oils the others were cream-colored, low-melting crystalline solids. 

A new class of pentacoordinate zwitterionic silicates (52-70) has been developed and reported by Tacke and his coworkers28-31 46-52 (cf Section II.A.3). These are generally high melting crystalline solids, which are almost insoluble in nonpolar organic solvents, and only slightly soluble in polar solvents. 

Compounds of type R3ASX2 are generally low-melting, crystalline solids, soluble in alcohol but only slightly soluble or insoluble in nonpolar solvents. These can readily be reduced to tertiary arsanes. They are hydrolyzed by water or alkali. Compounds containing at least one alkyl group yield on pyrolysis an alkyl halide and a haloarsane (49) ... 

These are white, high melting crystalline solids with NaCl type lattices. Calcium oxide, mp 2570°C, is made on a vast scale ... 

Borch prepared these reagents in about 85% yield by the reaction of orthoformate esters with boron trifluoride etherate in methylene chloride at —30° (3, 303). They are low-melting crystalline solids. Borch reported that these reagents are even more potent alkylating reagents than trialkyloxonium fluoroborates. 

As may be expected from their zwitterionic nature, the A, 5/-silicates la-7a and the X Ge-germanates lb-7b are high-melting crystalline solids All compounds are almost insoluble in unpolar solvents and exhibit very poor solubility in polar organic solvents. 

Difluorothianthrene, i.e., 2,7-difluoro-9,10-dithiaanthracene, c.f. Figure 5.8, is a monomer for poly(aryl ether thianthrene)s. This monomer is a high melting crystalline solid that sublimes under reduced pressure, simplifying the purification for polymer S5mthesis. It can be condensed with a bisphenol to yield poly(aryl ether thianthrene)s. ... 

At a phase transition, a material will suddenly transform from one state to another for example, a melting crystalline solid will go from a regular lattice structure to a disordered fluid. This transformation may have an energy associated with it, and we can define the heat of transformation Q ... 

In addition, 1,3-cyclohexadiene (4) and 1,3-cycIoheptadiene (27, 40) react to give the analogous complexes. All of the complexes are low-melting crystalline solids or liquids at ambient temperatures they may vary in color from pale yellow to deep orange. The complexes are thermally stable though a slow decomposition may occur on prolonged exposure to air. 

BMD s are high melting, crystalline solids, which crystallize readily from MeOH and EtOH. They are less polar than the parent steroid and possess a strong C-O-C band at 9. 0-9.4 microns. 124 For stereochemistry see Moreland, Cameron, Berg and Maxwell, reference 32. 

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