Heterocyclizations


SJ paracyclophane etc.] refers to the benzene rings in the structure, i.e. [8]-paracyclophane, [2,2,2]-para-cyclophane. Systems based upon heterocyclic molecules are also known.  [c.123]

Besides containing sulfur which is directly responsible for SO2 emissions, heavy fuels have significant amounts of nitrogen combined in complex heterocyclic structures. Figure 5.28 shows sulfur and nitrogen concentration ranges in vacuum residues (550°C ) as a function of the crude oil origin. Note that nitrogen contents between 3000 and 5000 ppm are common. Yet the European standards for NO emissions for combustion in industrial installations, set a maximum smoke threshold of 450 mg/Nm. In burners, the nitrogen oxides come from both nitrogen in the air and that contained in the  [c.269]

The aromatic extracts are black materials, composed essentially of condensed polynuclear aromatics and of heterocyclic nitrogen and/or sulfur compounds. Because of this highly aromatic structure, the extracts have good solvent power.  [c.291]

In the case of lubricant dispersants, the polar part is organic (amine, polyamine, heterocyclic nitrogen compounds, polyglycol).  [c.360]

A wide class of aiyl-based quaternary surfactants derives from heterocycles such as pyridine and quinoline. The Aralkyl pyridinium halides are easily synthesized from alkyl halides, and the paraquat family, based upon the 4, 4 -bipyridine species, provides many interesting surface active species widely studied in electron donor-acceptor processes. Cationic surfactants are not particularly useful as cleansing agents, but they play a widespread role as charge control (antistatic) agents in detergency and in many coating and thin film related products.  [c.2577]

Destabilization is observed in small rings such as three- and four-membered ring systems, due to bond angle strain. Interestingly, there is not much difference in ring strain of small rings between carbocyclic and heterocyclic structures containing carbon, oxygen, or nitrogen atoms, as shown in Figure 7-2 only rings containing sulfur atoms show less strain. Additional strain results from the introduction of multiple bonds into small rings. Medium-sized rings such as nine- and ten-membered ring systems are destabilized due to eclipsed conformations. Combinations of rings, particularly if small rings are involved, can introduce additional strain.  [c.326]

Decolorisation by Animal Charcoal. It sometimes hap pens (particularly with aromatic and heterocyclic compounds) that a crude product may contain a coloured impurity, which on recrystallisation dissolves in the boiling solvent, but is then partly occluded by crystals as they form and grow in the cooling solution. Sometimes a very tenacious occlusion may thus occur, and repeated and very wasteful recrystallisation may be necessary to eliminate the impurity. Moreover, the amount of the impurity present may be so small that the melting-point and analytical values of the compound are not sensibly affected, yet the appearance of the sample is ruined. Such impurities can usually be readily removed by boiling the substance in solution with a small quantity of finely powdered animal charcoal for a short time, and then filtering the solution while hot. The animal charcoal adsorbs the coloured impurity, and the filtrate is usually almost free from extraneous colour and deposits therefore pure crystals. This decolorisation by animal charcoal occurs most readily in aqueous solution, but can be performed in almost any organic solvent. Care should be taken not to use an excessive quantity  [c.21]

Heterocyclic and linear heteronuclear n conjugated systems pose a special problem because the heteroatom has an election density that is greater than or less than the election density of carbon. The Jacobi procedure suggests an empirical method of compensating for the increased electron density at, for example, nitrogen, in the way in which elements on the principal diagonal are built up by accretion during the iterative diagonalization procedure. If we place a nonzero element on the principal diagonal of the matrix to be diagonalized (after the xl matrix has been subtracted), when the accretion process is over that position will have an energy lower (or higher depending on the sign of the root) than it otherwise would have had.  [c.194]

One convention (Dickson. 1968) for oxygen heterocycles sets the coulomb integral at z 2f) and the resonance integral at Eor the oxirane moiety,  [c.199]

The physical properties of a number of aliphatic ethers are collected in Table 111,60. Some related heterocyclic compounds are included in the Table.  [c.316]

The reaction is applicable to the preparation of amines from amides of aliphatic aromatic, aryl-aliphatic and heterocyclic acids. A further example is given in Section IV,170 in connexion with the preparation of anthranilic acid from phthal-imide. It may be mentioned that for aliphatic monoamides containing more than eight carbon atoms aqueous alkaline hypohalite gives poor yields of the amines. Good results are obtained by treatment of the amide (C > 8) in methanol with sodium methoxide and bromine, followed by hydrolysis of the resulting N-alkyl methyl carbamate  [c.413]

This reagent affords compounds (1 1) with aromatic hydrocarbons and other classes of organic compounds (heterocyclic compounds, aromatic ethers, etc.).  [c.519]

SOME HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.828]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.829]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.831]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.833]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.835]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.837]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.839]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.841]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.843]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.845]

HETEROCYCLIC AND ALICYCLIC COMPOUNDS  [c.847]

A white solid, m.p. 178 C. Primarily of interest as a brominaling agent which will replace activated hydrogen atoms in benzylic or allylic positions, and also those on a carbon atom a to a carbonyl group. Activating influences can produce nuclear substitution in a benzene ring and certain heterocyclic compounds also used in the oxidation of secondary alcohols to ketones.  [c.69]

Jeanmaire D L and Van Duyne R P 1977 Part I heterocyclic, aromatic and aliphatic amines adsorbed on the anodized silver electrode J. Electroanal. Chem. 84 1-20  [c.1228]

The various fonns of betaines are very important for their charge control functions in diverse applications and include alkylbetaines, amidoalkylbetaines and heterocyclic betaines such as imidazolium betaines. Some surfactants can only be represented as resonance fonns having fonnal charge separation, although the actual atoms bearing the fonnal charge are not ftmctionally ionizable. Such species are mesoionic and an example of a trizaolium thiolate is illustrated in table C2.3.3.  [c.2578]

Figure C3.3.5 shows typical data obtained from experimental studies of tlie type described above, where tlie hot donor is tlie nitrogen heterocycle pyrazine, C Fl N, initially excited by an excinier laser to an energy of 40 640 Figure C3.3.5 shows typical data obtained from experimental studies of tlie type described above, where tlie hot donor is tlie nitrogen heterocycle pyrazine, C Fl N, initially excited by an excinier laser to an energy of 40 640
Each bond that matches one of these criteria is rated by a value between 0 (no strategic bond) and 100, which is the maximum rating for a strategic bond. Subse-quendy, the rating for each strategic bond is scaled relatively to the value of the highest-rated bond in the compound. As an example, the rating scheme for a heterocyclic compound is illustrated in Figure 10.3-40.  [c.582]

A wide variety of compounds similar in general type to (11a-d) but prepared from quinaldine methiodide or ethiodide for greater stability are used as photographic sensitisers. The /)-dimethylaminophenyl group can be replaced by various heterocyclic nitrogen systems, but in all these compounds the two nitrogen atoms must necessarily be linked through a conjugated system containing an odd number of carbon atoms to satisfy the above conditions. I hese compounds are known as cyanine dyes when added in trace quantities to a silver bromide-silver iodide emulsion on a photographic plate or film, the sensitit ity, t hich otherwise would be limited to the ultraviolet and visible violet and blue regions, may be extended well into the red region.  [c.303]

Styphnates. Aromatic hydrocarbons (and also some amines and heterocyclic bases) form 1 1-addition products with styphnic acid (2 4 6-trinitroresorcinol),  [c.519]


See pages that mention the term Heterocyclizations : [c.28]    [c.41]    [c.49]    [c.121]    [c.202]    [c.255]    [c.255]    [c.284]    [c.293]    [c.322]    [c.341]    [c.382]    [c.404]    [c.30]    [c.326]    [c.317]    [c.373]    [c.342]    [c.561]    [c.691]   
Thiazole and its derivatives Ч.2 (1979) -- [ c.58 , c.65 , c.93 , c.105 , c.118 ]