Structure of Compounds

Inductive learning has been the major process of acquiring chemical knowledge from the very beginnings of chemistry - or, to make the point, alchemy. Chemists have done experiments, have made measurements on the properties of their compounds, have treated them with other compounds to study their reactions, and have run reactions to make new compounds. Systematic variations in the structure of compounds, or in reaction conditions, provided results that were ordered by developing models. These models then allowed predictions to be made. 

The principal reactions of this class of compounds are summarized in Scheme 172. In most of these reactions the reactive nucleophilic center is the terminal NHj group, although the other exocyclic nitrogen may also be involved, as shown by acetylation, which yields 284 and 285. However, the structure of compound 281 is not the one proposed in a recent report (1582) that attributes the attack to the other exocyclic nitrogen. The formation of osazones (287) from sugars, 2-hydrazinothiazoles, and hydrazine has been reported (525, 531). 

Compound A (C4H10) gives two different monochlondes on photochemical chlorination Treatment of either of these monochlondes with potassium tert butoxide in dimethyl sulfoxide gives the same alkene B (CaHg) as the only product What are the structures of compound A the two monochlondes and alkene B2... 

Compounds A and B are isomers of molecular formula C9Hi9Br Both yield the same alkene C as the exclusive product of elimination on being treated with potassium tert butoxide in dimethyl sulfoxide Hydrogenation of alkene C gives 2 3 3 4 tetramethylpentane What are the structures of compounds A and B and alkene C2... 

Allene can be converted to a tnmer (compound A) of molecular formula C9H12 Compound A reacts with dimethyl acetylenedicarboxylate to give compound B Deduce the structure of compound A... 

A certain compound A when treated with N bromosuccinimide and benzoyl peroxide under photochemical conditions in refluxing carbon tetrachloride gave 3 4 5 tnbromobenzyl bromide in excellent yield Deduce the structure of compound A... 

Compounds A and B are isomenc diketones of molecular formula CgHjQ02 The H NMR spectrum of compound A contains two signals both singlets at 8 2 2 (six protons) and 2 8 (four protons) The H NMR spectrum of compound B contains two signals one at 8 1 3 (triplet six protons) and the other at 8 2 8 (quartet four protons) What are the structures of compounds A and B" ... 

The ketone shown was prepared in a three step sequence from ethyl trifluoroacetate The first step in the sequence involved treating ethyl tnfluoroacetate with ammonia to give a compound A Compound A was in turn converted to the desired ketone by way of a compound B Fill in the missing reagents in the sequence shown and give the structures of compounds A and B... 

The structure of compound A was established in part by converting it to known compounds Treat ment of A with excess methyl iodide in the presence of silver oxide followed by hydrolysis with dilute hydrochlonc acid gave a tnmethyl ether of D galactose Companng this trimethyl ether with known trimethyl ethers of D galactose allowed the structure of compound A to be deduced... 

Fig. 1. Structures of compounds in petroleum cmde oils. See Table 1.

Table 1 X-Ray Structures of Compounds with Five-membered Rings and Two, Three or Four Heteroatoms ...

Fig. 2.3. The crystal structure of the "intermetollic" compound CuAlj. The structures of compounds are usually more complicated than those of pure metals.

Under conditions of photochemical chlorination, (CH3)3CCH2C(CH3)3 gave a mixture of two monochlorides in a 4 1 ratio. The structures of these two products were assigned on the basis of their S l hydrolysis rates in aqueous ethanol. The major product (compound A) underwent hydrolysis much more slowly than the minor one (compound B). Deduce the structures of compounds A and B. 

The simple methyl compounds do indeed contain methyl groups, e.g., methylthiazoles exist as such and not in the methylene form."" The structures of compounds of the pyrophthalone type containing a benzimidazole and benzthiazole nucleus, e.g. 228, have been discussed. Bis (benzimidazolyl) methanes (229) absorb light in the... 

I he potent antiinflammatory action exerted by many aryl acetic acid derivatives has led to the continued exploration of this class. It is apparent from a consideration of the structures of compounds that have become prominent that considerable structural latitude is possible without loss of activity. 

Structure ofF Although F has never been obtained in a completely pure state, the FAB mass spectral data of F [m/z 687 (M + Na)+ and 665 (M+H)+], and the comparison of the H and 13C NMR spectra of F with those of Oxy-F, suggested structure 6 for this compound. To confirm this structure, F was subjected to ozonolysis, followed by diazomethane treatment. The expected diester 5 was successfully isolated, indicating that 6 is indeed the structure of compound F (Nakamura et al., 1988). The structure of the luminescence reaction product of F is considered to be 8 on the basis of comparison with the dinoflagellate luminescence system (see Chapter 8). 

Fig. 3.2.6 Chemical structures of compound F (6 the euphausiid luciferin), a product obtained when F was left standing at -20°C for 2 weeks (7), and the product of bioluminescence reaction (8).

Structure of Compounds Containing Chain s of Sulfur Atoms... 

Electrospray is an unusual mass spectrometry technique in that it allows the study of the three-dimensional structure of compounds, particularly proteins, in solution as it is believed that this is relatively unchanged when ions are transferred to the vapour phase. This type of application will be discussed in more detail in Chapter 5 but attention is drawn at this point to the previous comments regarding the effect that the HPLC conditions, such as pH, may have on the appearance of an electrospray spectrum and the conformational deductions that may be made from them. 

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