Isomeric products

In a search for fluorocarbons having anesthetic properties 1 2 dichloro 1 1 difluoropropane was subjected to photochemical chlorination Two isomeric products were obtained one of which was identified as 1 2 3 tnchloro 1 1 difluoropropane What is the structure of the second com pound" ... 

Chlorination of 2 butanone yields two isomeric products each ) having the molecular formula C4H7CIO Identify these two compounds I... 

When compound A is heated two isomeric products are formed What are these two products ... 

These reactions involve the intermediate formation of thiols, followed by condensation to the sulfides. The observation of isomerized products in suitable cases indicates the intermediate formation of carbocations, either by protolysis of alkanes by the superacid or reversible ionisation of the thiol products (149). 

Dinitration of toluene results in the formation of a number of isomeric products, and with a typical sulfuric—nitric acid nitrating mixture the following mixture ofisomers is obtained 75 wt % 2,4-dinitrotoluene [121-14-2] 19 wt % 2,6-dinitrotoluene [606-20-2], 2.5 wt % 3,4-dinitrotoluene [610-39-9], 1 wt %... 

Although the yields are variable and isomeric products are obtained using unsymmetrical ethenes, the reaction conditions are mild and show promise of stereoselectivity. 

Recognition of the thio group s key role in biochemistry has led to studies of l,4-ben2oquinone with glutathione, a tripeptide 7-Glu-Cys-Gly (GSH). The cross-oxidation of the initial addition product by excess quinone leads, under physiological conditions, to all three isomeric products (46), ie, the 2,3-and 2,6-isomers as well as the 2,5-disubstituted l,4-ben2oquinone shown. 

It appears that only l-phenyltetra2ole-5-thiol (HSPT) (56) produces all three isomeric products when the initial hydroquinone product is further oxidi2ed and a second thiol is added (47). 

Fig. 3. Photochemical and thermal isomerization products of vitamin D manufacture (49). The quantum yields of the reactions ate hsted beside the arrows...

IR spectroscopy has also been used in structural problems in 2- and 3-hydroxypyrido[3,4-f ]pyrazines (63JCS5156), in 8-oxopyrido[2,3-f ]pyrazine-7-acids (73MI21501) and in the pyrido[3,4-f ]quinoxaline field (74JCS(P1)1965). IR spectra were recommended for the distinction of isomeric products in the Isay reaction (Section 2.15.15.6.1) (71TH21500) UV spectra were not satisfactory. The Raman spectra of a number of 1- and 3-deazaflavin analogues have been recorded and discussed (80BBA(623)77). 

Azoles containing a free NH group react comparatively readily with acyl halides. N-Acyl-pyrazoles, -imidazoles, etc. can be prepared by reaction sequences of either type (66) -> (67) or type (70)->(71) or (72). Such reactions have been carried out with benzoyl halides, sulfonyl halides, isocyanates, isothiocyanates and chloroformates. Reactions occur under Schotten-Baumann conditions or in inert solvents. When two isomeric products could result, only the thermodynamically stable one is usually obtained because the acylation reactions are reversible and the products interconvert readily. Thus benzotriazole forms 1-acyl derivatives (99) which preserve the Kekule resonance of the benzene ring and are therefore more stable than the isomeric 2-acyl derivatives. Acylation of pyrazoles also usually gives the more stable isomer as the sole product (66AHCi6)347). The imidazole-catalyzed hydrolysis of esters can be classified as an electrophilic attack on the multiply bonded imidazole nitrogen. 

Scheme 4 also represents the classical route to isoxazoles, first studied in 1888 by Claisen and his coworkers (1888CB1149). Reaction of a 1,3-diketone with hydroxylamine gives, via the isolable monoxime (108) and the 4-hydroxyisoxazole (109), the isoxazole (110). Unsym-metrical 1,3-diketones result in both possible isomers (110) and (111), but the ratio of the isomeric products can be controlled by the right combination of the 1,3-dicarbonyl component and the reaction conditions used. These important considerations are described in Chapter 4.16, along with the variations possible in the 1,3-dicarbonyl component designed to yield diverse substituents in the resultant isoxazole. 

However, depending on the nature of the initial heterocycle, rearrangements are possible. Alkylation of thiazole to form the thiazolium salt (390) and generation of the ylide (391) with triethylamine in the presence of DMAD gave not (392) but the isomeric product (393) by the rearrangement indicated (76JOC187). Rearrangements of these types are described in Chapters 4.07 and 4.19. 

The 6a-halo- and 6,6-dihalo-penicillanates have been shown to undergo halogen-metal exchange to form enolates which can then react with acetaldehyde to form 6-(l-hydroxyethyOpenicillanates (Scheme 34) (77JOC2960, 79TL3805). From (41) the isomeric products were obtained in the ratio (48) (49) (50) = 24 49 27. From (42) the isomeric products were obtained in the ratio (51) (52) (53) = 39 1.5 60. Product ratios were very... 

Pyridone also catalyzes epimerization of the anomeric position of the tetramethyl ether of glucose. The mechanism involves two double proton transfers. The first leads to a ring-opened intermediate, and the second results in ring closure to the isomerized product ... 

Treatment of D-mannose with methanol in the presence of an acid catalyst yields four isomeric products having the molecular formula C7H14O6. What are these four products ... 

Indolization of 3-substituted phenylhydrazone 59 normally gives rise to two isomeric products, 4-substituted indole 60 and 6-substituted indole 61. The ratio of 60 to 61 from the cyclization depends on the nature of the R group, the structure of the carbonyl... 

The /neta-substituted anilines provide one or two isomeric products depending on the nature of the substituents (vide infra). 

Methyl-3-re-propylindole (43) was obtained by hydrogenation of the intermediate 2-methyl-3-allylindole (44), obtained by the allylation of 2-methylindole magnesium iodide. There were no reports of isomeric products being formed in this reaction. ... 

Ganellin and Ridley obtained a mixture of isomeric products by the action of 2-ehloro-l dimcthylaminopropane on indole magnesium iodide. In this case both 3-(2-dimethylamino-l-methylethyl)... 

Dimethylthiophene reacts photochemically with rran.s-Rh(PMe3)2(CO)Cl to yield the isomeric products 218 (R = Me) and 219 because of C—H activation of thiophene (960M872) as well as species 220 (R = Me). Unsubstituted thiophene in similar conditions gives five products, the 3-thienyl activated isomers 218 (R = H) and 219 (R = H), the 2-thienyl isomers, 221 and 222, and 2-thienyl analogs of 220 (R = H). 

In contrast to alkoxides, thiolates react with 3,4-bis(arylsulfonyl)furoxans to give both isomeric products 283 and 284 (Scheme 185) (96JHC327, 97JMC463). 

In contrast, when the irradiation is performed on 2-cyanopyrrole, the isomeric products are observed. In fact, in this case, the corresponding Dewar pyrrole shows a lower energy than in the previous case, allowing the formation of the isomeric products (Fig. 6). When 2-methylpyrrole is used as substrate, the formation of the triplet state is favored, but this triplet state cannot evolve through the formation of the biradical intermediate. 

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