Nitrogen aromatic imides

The imides, primaiy and secondary nitro compounds, oximes and sulphon amides of Solubility Group III are weakly acidic nitrogen compounds they cannot be titrated satisfactorily with a standard alkaU nor do they exhibit the reactions characteristic of phenols. The neutral nitrogen compounds of Solubility Group VII include tertiary nitro compounds amides (simple and substituted) derivatives of aldehydes and ketones (hydrazones, semlcarb-azones, ete.) nitriles nitroso, azo, hydrazo and other Intermediate reduction products of aromatic nitro compounds. All the above nitrogen compounds, and also the sulphonamides of Solubility Group VII, respond, with few exceptions, to the same classification reactions (reduction and hydrolysis) and hence will be considered together. 

The well known thermally induced isomerization of an isoimide to an imide was the chemistry selected to test the concept. A series of high molecular weight polyisoimides was prepared based on PMDA and pendent aromatic diamines that on thermal treatment would exhibit the required geometry for reinforcement. Polymerizations of the diamines with PMDA were carried out in DMAC (10% by weight) at room temperature in a dry nitrogen atmosphere. Subsequent cyclodehydration of the polyamic acid to the corresponding polyisoimide was... 

The thermo-oxidative stability of a silane where silicon is linked to imide nitrogen by an aromatic radical (CA-25) was greater than that of a compound where silicon is linked to nitrogen by an aliphatic group (CA-11). Upon... 

Electronically excited carbonyl chromophores in ketones, aldehydes, amides, imides, or electron-deficient aromatic compounds may act as electron acceptors (A) versus alkenes, amines, carboxylates, carboxamides, and thioethers (D, donors). In addition, PET processes can also occur from aromatic rings with electron-donating groups to chloroacetamides. These reactions can be versatile procedures for the synthesis of nitrogen-containing heterocyclic compounds with six-membered (or larger) rings [2],... 

Food, flavors consist of numerous compounds, none of which alone is characteristic of specific food. Classes of compounds which emcompass food flavors are - hydrocarbons (aliphatic, ali-cyclic, aromatic) carbonyls (aldehydes, ketones) carboxylic acids, esters, imides, anhydrides alcohols, phenols, ethers alkylamines, alkylimines aliphatic sulfur compounds (thiols, mono-, di- and tri-sulfides) nitrogen heterocyclics (pyrroles, pyrazines, pyridines) sulfur heterocylics (thiophenes, thiazoles, trithiolane, thialidine) and oxygen-heterocyclics (lactone, pyrone, furan). Discussion will be limited to striking developments in heterocyclics. 

Chlorine in 2-chlorolepidine (21) is very reactive, since the compound can be considered an imide chloride. It is readily replaced by hydrogen to form lepidine (22 equation 48). Similarly (23) is converted to (24) on catalytic hydrogenation (equation 49). The above reductions may be applied to many six-membered aromatic heterocycles containing chlorine on the carbon next to nitrogen thus pyridones,... 

Phosgene is a suitable reagent for converting secondary amides and N-unsubstituted lac-tams to imide chlorides, e.g. (195) and (196) (Scheme 27). The substituents at nitrogen might be saturated aliphatic or aromatic groups, but even unsaturated groups seem to be possible. The reaction,... 

C. Heteroaromatic N-Imides. In this class of azomethinimines, the formal C==N bond of the 1,3-dipole is incorporated into a heteroaromatic ring system. Cycloaddition to a dipolarophile is accompanied by loss of aromaticity in the nitrogenous ring, which reduces the 1,3-activity as well as the stability of the triazoline adduct (77LA498, 77LA506). 

The thermal and oxidative stability of polyimides is thonght to be related to the combination of both the five-membered cyclic imide ring and the natnre of the aromatic ring directly connected to the nitrogen (Figure 6). 

AcOH, H2O, DMF, 110°C, 79% yield. In this case the TIPS group was removed from an imide nitrogen. In this case a PMB group could not be cleaved because of the easily oxidized aromatic diamine. 

In a study of model compounds Ishida (2) showed that the tail is intrinsic to the pyromellitimide moiety and that the center of the peak associated with the tail became red shifted with the degree of conjugation provided by the substituents at either end of an N,N -pyromellitimide. The absorption maximum red shifted from 345 nm to 356 nm in going from cyclohexyl to phenyl substitution and further to 371 nm with substitution of phenoxyphenyl. Furthermore, upon aromatic substitution the imide nitrogen changed its electronic character from tetrahedral- sp3 to planar- sp2. This shift of the absorption maximum to longer wavelength is consistent with an increase in electron delocalization afforded the pyromellitimide moiety with aromatic... 

Phenyl groups bonded to the Imide nitrogen atom usually appear as a single, relatively sharp band near 7.4 ppm. The four aromatic hydrogens of the Phthalimides are observed as a symmetrical, higher-order series of bands centered at about 7.8 ppm. 

The C-N bonds of the imide rings were identified as primary decomposition sites during the pyrolysis of Kapton. The resulting structures can be described best as amide groups. The next step is the decomposition of the aromatic systems. Simultaneously -C=N and -C=C- groups are formed as intermediates. The last step of the decomposition is the elimination of the carbonyl groups. A carbon- and nitrogen-rich residue remains. 

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