DABA

Bismaleimide Resins via EI E Reaction. The copolymerization of a BMI with o,o -diallylbisphenol A [1745-89-7] (DABA) is a resia coacept that has beea widely accepted by the iadustry because BMI—DABA bleads are tacky soHds at room temperature and therefore provide all the desired properties ia prepregs, such as drape and tack, similar to epoxies. Crystalline BMI can easily be blended with DABA, which is a high viscosity fluid at room temperature. Upon heating BMI—DABA blends copolymerize via complex ENE and Diels-Alder reactions as outlined ia Eigure 8. 

The mixed-donor tridentate ligands bis[2-diphenylphosphino)ethyl] benzylamine (dpba) and bis[2-(diphenylarsino)ethyl] benzylamine (daba) form square-planar complexes with IrCl and IrPPh3 moieties.664... 

Irradiation of a benzene solution of DABA at room temperature with a nitrogen laser (Horn and Schuster, 1982) gives the transient absorption spectrum shown in Fig. 3. This spectrum was recorded 50 ns after irradiation of the diazo-compound and decays over a period of ca 250 ps by a path exhibiting complex kinetic behavior. This transient spectrum is essentially identical with the low temperature optical spectrum described above, and thus is similarly assigned to 3BA. 

Irradiation of DABA at room temperature with a mode-locked frequency... 

Fig. 3 Transient absorption spectrum recorded 50 ns after irradiation of DABA in benzene solution. The region between 370 and 440 nm is obscured by the absorption of the diazo compound...

Examination of DABA photolysis in cyclohexane instead of benzene solution leads to predictably different results. The laser spectroscopy shows that 3BA is formed but, in this solvent, the triplet carbene undergoes an additional rapid reaction to generate the mesitylbora-anthryl radical (BAH ). This radical is identified by comparison of its spectrum with that of an authentic sample prepared from dihydrobora-anthracene. The half-life of... 

The products obtained from photolysis of DABA in cylcohexane support the assignments made above. The major product is the dimer formed from the coupling of BAH. This is accompanied by the other expected radical products, dihydrobora-anthracene and cyclohexybora-anthracene, as is shown in (19). 

The transient triplet carbene formed from irradiation of DABA in benzene can be observed to react with styrene. For this process laser spectroscopy reveals a bimolecular rate constant (ksty) equal to 1.2 x 107M-1s-1. The product of the reaction is the expected cyclopropane. This observation clearly supports the spectral assignment of the carbene made above. When deuteriated a-methylstyrene is substituted for styrene as a trap for the carbene, the cyclopropane that results is a 1 1 mixture of stereoisomers, (20) (Table 6). This finding indicates that BA is reacting in this sequence exclusively from its ground triplet state. 

The reaction of BA with isopropyl alcohol is particularly revealing. Direct irradiation of DABA in neat isopropyl alcohol gives the ether (17%) expected from the reaction of the singlet carbene, and the radical coupling products characteristic of the triplet spin state (21). The ratio of the yields of radical-derived products to ether depends inversely on the concentration of isopropyl alcohol in a benzene solution. This behavior is particularly meaningful when compared with that of FL, XA and DPM. For these... 

The triplet-sensitized irradiation of DABA in neat isopropyl alcohol does not give a detectable amount of the ether. For comparison, triplet sensitization of DAF or DAX (see below) gives the appropriate ethers in a high yield which is essentially unchanged from the direct irradiation. 

Similarly, direct irradiation of DABA in neat isopropyl alcohol generates... 

The significance of a value of AG 5.2 kcal mol -1 is that most of the bimolecular reactions of the triplet carbene will be faster than the formation of the singlet from the triplet. Thus intersystem crossing from BA to 3BA is irreversible, and if 3BA is formed first (triplet sensitization), then there will be no reaction at all of BA. However, in the direct irradiation of DABA, some... 

Diaminobenzoic acid (DABA) reacts with aldehydes of the form RCH CHO to produce a strongly fluorescent compound. Acid-catalysed removal of the purine base from the nucleic acid exposes the 1 and 2 carbons of deoxyribose... 

Zeolite/polymer mixed-matrix membranes prepared from crosslinked polymers and surface-modified zeolite particles offered both outstanding separation properties and swelling resistance for some gas and vapor separations such as purification of natural gas. Hillock and coworkers reported that crosslinked mixed-matrix membranes prepared from modified SSZ-13 zeolite and 1,3-propane diol crosslinked polyimide (6FDA-DAM-DABA) synthesized from 2,2 -feis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, p-dimethylaminobenzylamine-and 3,5-diaminobenzoic acid displayed high CO2/CH4 selectivities of up to 47 Barrer and CO2 permeabilities of up to 89 Barrer under mixed gas testing conditions [71]. Additionally, these crosslinked mixed-matrix membranes were resistant to CO2 plasticization up to 450 psia (3100kPa). 

The maleimide group can undergo a variety of chemical reactions. The reactivity of the double bond is a consequence of the electron withdrawing nature of the two adjacent carbonyl groups which create a very electron-deficient double bond, and therefore is susceptible to homo- and copolymerizations. Such polymerizations may be induced by free radicals or anions. Nucleophiles such as primary and secondary amines, phenates, thiophenates, carboxylates, etc. may react via the classical Michael addition mechanism. The maleimide group furthermore is a very reactive dienophile and can therefore be employed in a variety of Diels Alder reactions. Bisdienes such as divinylbenzene, bis(vinylbenzyl) compounds, bis(propenylphenoxy) compounds and bis(benzocyclobutenes) are very attractive Diels Alder comonomers and therefore some are used as constituents for BMI resin formulations. An important chemical reaction of the maleimide group is the ENE reaction with allylphenyl compounds. The most attractive comonomer of this family is DABA particularly when tough bismaleimide resins are desired. 

The resonance Raman spectrum of a similar complex has been reported, that of a ternary complex of LADH, NADH and 4-(7V 7V-dimethylamino)benzaldehyde (DABA) with the disappearance of the carbonyl stretching frequency of the DABA at 1664 cm-1 also indicating strongly that inner sphere complexation of the substrate occurs, the zinc withdrawing electron density from the aldehyde oxygen forming a zinc-oxygen coordinate bond.1397... 

Zelcans, G., Lukevics, E. Silicijs dzivaja daba, Riga, 1976... 

The trisazo dyes include in particular blue, green, and black grades. Diamines used are 4,4 -diaminobenzanilide (DABA) and 4,4 -diaminodiphenylaminc-2-sul-fonic acid (DADPS). The most important synthetic principle in this range is the type K i<— Di- K2<— D2. The sequence of the three couplings depends on the nature of the components. 

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