Facial form

The localized-valence halogen-bridged platinum(II)/platinum(IV) complexes (175) are of interest because of their highly anisotropic electrical and optical properties. The complexes are characterized by broad and intense intervalence bands in their electronic spectra.542 Partial oxidation of [PtCl(dien)]Cl with iodine yields the mixed valence species [PtI(dien)][PtI3(dien)]I2,543 but when 4Me-dien is used, the mixed valence compound is only obtained if it is trapped quickly, before isomerization of the meridional platinum(IV) complex to a facial form.544 Although these species nominally have localized valences, the extent of delocalization increases as the bridging halide... 

Draw rough Distance from Facial form Kidneys Intestine... 

For the mixed ligand complex with l- or D-aspartic acid and L-2,4-diaminobutyric acid, [Co(l- or D-asp) (L-2,4-dba)], the possible isomers are shown in Fig. 3.11. Both of L- and D-series are composed of two meridional forms and one facial form about the [Co(N)3(0)3] chromophore. The two L-mer isomers are denoted by L-tranjOs-cisNs (with respect to oxygen) and L-cisOstronjNs. To investigate the H NMR spectra of those isomers, Watabeetal. prepared the complexes with Na3[Co(C03)3] 3 H2O... 

Fig. 1 The main four facial forms described by Leon...

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

The ASA (now ANSI) performance code for Safety Glazing Materials was revised in 1966 to incorporate these improvements in windshield constmction. The addition of test no. 26 requiring support of a 2.3-kg ball dropped from 3.7 m defined this level of improvement. It was based on a correlation estabUshed between 10-kg, instmmented, head-form impacts on windshields, on 0.6 x 0.9-m flat laminates, and the standard 0.3 x 0.3-m laminate with the 2.3-kg ball (28). Crash cases involving the two windshield interlayer types were matched for car impact speeds and were compared (29). The improved design produced fewer, less extensive, and less severe facial lacerations than those produced in the pre-1966 models. 

Tinted dry powders form the second type of facial makeup. Commonly, the blended soHds are compressed into compacts. The finished products, sold as compressed powders, rouges, or blushers, are appHed to the face with the aid of powder puffs, bmshes, or similar devices. Facial makeup compositions have been pubHshed for rouge (57), powder (58), and makeup (59). 

The second C-C bond forming step (step C), while occurring after the first irreversible ee determining step (step B), can affect the observed enantioselective outcome of the reaction. If the radical intermediate collapses without rotation (k3 Ict, k5 ke), then the observed ee would be determined by the first C-C bond forming step (ki vs. k2), that is the facial selectivity (Scheme 1.4.6). However, if rotation is allowed followed by collapse, then the rate of both trans pathways (Ic and k ) will proportionally effect the observed ee of the cis epoxide (ks vs. ks). Should bond rotation be permissible, the diastereomeric nature of the radical intermediates 9a and 9b renders the distinct possibility of different observed ee s for frany-epoxides and dy-epoxides. 

The formation of the tran -aziridine 281 as the major product of the conjugated addition of benzylamine to the furanone 280 was rationalized in terms of selective facial protonation of the initially formed enol 284 (Scheme 75) (00TL3061). 

It forms a semi-carbazone melting at 136° to 138°, which can be obtained as follows Ten c.c. of methyl-heptenone are dissolved in 20 c.c. of facial acetic acid, and a mixture of 10 grams of semi-carbazide hydrochloride and 15 grams of sodium acetate dissolved in 20 c.c. of water is added. After half an hour the semi-carbazone is precipitated by the addition of water, and recrystalUsed from dilute alcohol. 

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

Edman and Simmons [146] synthesized bicyclo[2.2.1]hepta-2,5-diene-2,3-dicar-boxylic anhydride 80 as a facially perturbed dienophile on the basis of the norbornadiene motif, and its top selectivity in Diels-Alder reactions with cyclopentadiene (top-exo top-endo = 60 70 1) was observed by Bartlett (Fig. 14) [147], The most preferred addition was top-exo addition, along with the minor addition modes, top-endo bottom-enrfo addition (Fig. 14). The addition of butadiene to this anhydride preferentially afforded the top-adduct (top bottom = 6 1). In the addition of anthracene, a top-adduct was formed exclusively. 

Epstein-Barr virus (EBV) Enveloped, icosahedral particles 150nm in diameter Infections occur by salivary exchange. In young children they are commonly asymptomatic but the virus persists in a latent form in lymphocytes. Infection delayed until adolescence often results in glandularfever. In tropical Africa, a severe EBV infection early in life predisposes the child to malignant facial tumours (Burkitt s lymphoma)... 

The compact bicyclic lactams 15 and 16 are examples of chiral systems that show high facial selectivity. Interestingly, 15 is alkylated from the convex face. When two successive alkylations are done, both groups are added from the endo face, so the configuration of the newly formed quaternary center can be controlled. The closely related 16 shows exo stereoselectivity. 100... 

Stereochemical Control by the Aldehyde. A chiral center in an aldehyde can influence the direction of approach by an enolate or other nucleophile. This facial selectivity is in addition to the simple syn, anti diastereoselectivity so that if either the aldehyde or enolate contains a stereocenter, four stereoisomers are possible. There are four possible chairlike TSs, of which two lead to syn product from the Z-enolate and two to anti product from the A-enolate. The two members of each pair differ in the facial approach to the aldehyde and give products of opposite configuration at both of the newly formed stereocenters. If the substituted aldehyde is racemic, the enantiomeric products will be formed, making a total of eight stereoisomers possible. 

Stereochemical Control Through Chiral Auxiliaries. Another approach to control of stereochemistry is installation of a chiral auxiliary, which can achieve a high degree of facial selectivity.124 A very useful method for enantioselective aldol reactions is based on the oxazolidinones 10,11, and 12. These compounds are available in enantiomerically pure form and can be used to obtain either enantiomer of the desired product. 

In Entry 11 the dienophile is an a-methylene lactam. As noted for this class of dienophiles, the stereoselectivity results from preferred exo addition (see p. 471). The reaction in Entry 12 was used in an enantiospecific synthesis of estrone. The dienophile was used in enantiomerically pure form and the dioxolane ring imparts a high facial selectivity to the dienophile. The reaction occurs through an endo TS. 

The reaction in Entry 13 is completely regioselective and both stereoisomers are formed through an endo TS. The two stereoisomers result from competing facial approaches to the diene. 

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