AIBN 2,2 -Azobis

Azo compounds having functional groups that stabilize the radical products are especially reactive. The stabilizing effect of the cyano substituent is responsible for the easy decomposition of azobis(isobutyronitrile) (AIBN), which is frequently used as a radical initiator. 

BZ2O2 = benzoyl peroxide AIBN = 2,2 -azobis-2-(methylpropionitnle)... 

ACPA azobis(4-cyanopentanoic acid) AIBN azobis isobutyronitrile) BPO benzoyl peroxide DVB divinyl benzene, EGA 2-ethylcyano-acrylate HPC hydroxypropyl cellulose MMA methyl methacrylate PAAc polyacrylic acid PEI polyethyleneimine, PEO/PPO polyethylene oxide/polypyropylene oxide copolymer PVME polyvinylmethylether PVP polyvinylpyrrolidone K-30 DMSO dimethylsulfoxide PGA polyglutaraldehyde CMS chloromethylstyrene PMMA-g-OSA polymethylmethacrylate grafted oligostearic acid. 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

To incorporate a labile azo group as the essential active site to MAI, a series of azo compounds such as 2,2 azobisisobutyronitrile (AIBN), 4,4 -azobis(4-cyanopen-tanoyl chloride) (ACPC), 2,2 azobis (2-cyanopropanol) (ACPO), 2,2 azobis [2-methyl-N-(2-hydroxyethyl)prop-ionamide] (AHPA), etc., were used as starting materials for polycondensation with various diols, diamines, diacids, or diisocyanates. 

Ueno and coworkers10 have found that the facile displacement of sulfonyl group from a-alkylated allyl p-tolyl sulfones 18 by tri-n-butyltin radical in the presence of 2,2 -azobis[2-methylpropanenitrile] (AIBN) occurs smoothly in refluxing benzene (equation 11). In contrast, vinyl sulfones undergo the radical substitution reaction to give vinylstannanes in the presence of AIBN at a higher temperature11. 

Acetylated 1-thioaldoses react with alkenes in the presence of azobis(isobuty-ronitrile) (AIBN) to give acylated alkyl 1-thioglycosides.55... 

Monomers were mixed in the desired ratios (Table 1) in a round-bottomed flask. The resulting mixtures (5g) were diluted with cyclopentanone (45 g). Azobis(isobutyronit-rile) (AIBN) (0.18 g, 3% w/w with respect to the monomer mixture) was then added. The resulting solution was degassed, put under nitrogen, and placed for 48 h in a thermostated oven preheated at 80 °C. The polymerization solution was concentrated to about half of the original volume and subsequently poured in the fivefold volume of diethylether under efficient stirring. The precipitated solid was filtered off and dried under vacuum to constant weight. Isolated yields were about 80% in all cases. 

The preparation of tetramethylsuccinonitrile by decomposition at 90-92°C in azobis-isobutyronitrile (AIBN) heptane gives rise to a detonation. The medium was not stirred and the accident is related to the instability of this diazoic compound, which had probabiy accumulated (the nitrile groups are not responsible for it). If AIBN Is introduced into heptane slowly, at 90°C and under vigorous stirring, the reaction seems safer. 

To conclusively disprove the involvement of the chromanol methide radical, the reaction of a-tocopherol with dibenzoyl peroxide was conducted in the presence of a large excess of ethyl vinyl ether used as a solvent component. If 5a-a-tocopheryl benzoate (11) was formed homolytically according to Fig. 6.6, the presence of ethyl vinyl ether should have no large influence on the product distribution. However, if (11) was formed heterolytically according to Fig. 6.9, the intermediate o-QM 3 would be readily trapped by ethyl vinyl ether in a hetero-Diels-Alder process with inverse electron demand,27 thus drastically reducing the amount of 11 formed. Exactly the latter outcome was observed experimentally. In fact, using a 10-fold excess of ethyl vinyl ether relative to a-tocopherol and azobis(isobutyronitrile) (AIBN) as radical... 

N-4-(Pyridyl) bis(methacrylimide) (8.6 g, 37 mmol) was dissolved in dimethylformamide (35 ml). The solution was degassed under argon and azobis(isobutyronitrile) (0.4 g, 2 mmol) was added. The reaction mixture was heated to 75°C under argon. After 24 hrs, another portion of AIBN (0.4 g, 2 mmol) was added and the reaction continued for another 24 hrs. The resulting polymer was isolated by precipitation from ether in 65% yield. DSC of the polymer indicated a Tg at 110°C. TGA showed onset of... 

Radical cyclization of perhydro-l,3-benzoxazines 518, promoted by Bu vSnI I in the presence of 2,2 -azobis(2-methylpro-pionitrile) (AIBN) gave a mixture of perhydropyrido[2,T ][l,3]benzoxazin-9-ones 519 and 520 and the seven-membered tricyclic derivatives 521 and 522, formed by a 6-exo- and a 7-rwr/o-cyclization process, respectively (Scheme 54) < 1999TL2421 >. Cyclization of parent acrylamide 518 (R = R1 = H) occurred with moderate regioselectivity (()-exo/7-endo ratio = 65 35) and poor stereoselectivity (519/520 ratio = 42 43). The presence of a [1-methyl group in crotylamide 518 (R = Me, R1 = H) disfavored the 7-/w/ -cyclization process, but did not influence the stereoselectivity of the cyclization (519/520 ratio = 66 34). The presence of an a-methyl group in methylacrylamide 518 (R=H, R1 Me) caused a retardation of the 6-oeo-attack, favoring the 7-/w/ -cyclization with a higher stereoselectivity (521/522 ratio = 75 12). 

A3 AIBN c Cp DLS DLVO DSC EO GMA HS-DSC KPS LCST Osmotic third virial coefficient 2,2 -Azobis(isobutyronitrile) Polymer concentration Partial heat capacity Dynamic light scattering Derjaguin-Landau-Verwey-Overbeek Differential scanning calorimetry Ethylene oxide Glycidylmethacrylate High-sensitivity differential scanning calorimetry Potassium persulphate Lower critical solution temperature... 

The EtsSiH/tetracyanoethylene combination reduces acetals and ketals to the corresponding ethers but the yields are mixed.500 The full reduction of benz-aldehyde acetals to the toluene derivatives is realized by the initial reduction with Et3SiH/SnBr2-AcBr followed by Bu3SnH/AIBN (azobis(isobutyronitrile)) or LiAlH4.479 The overall yields are excellent. 

By using lipophilic initiators, such as 2,2 -azobis(isobutyronitrile) (AIBN), in the micro-ECP, diffusion of monomers is too slow compared with the reaction rate. Therefore, copolymerization is confined to the incoherent, lipophilic phase [112,113] and very small microgel particles with a rather uniform size result. 

Semitelechelic HPMA polymers were synthesized by free radical polymerization of HPMA using 2,2 -azobis(isobutyronitrile) (AIBN) as the initiator and alkyl mercaptans as chain transfer agents. Alkyl mercaptans with different functional groups, namely, 2-mercaptoethylamine, 3-mercapto-propionic acid, 3-mercaptopropionic hydrazide, and methyl 3-mercapto-propionate, were used as the chain transfer agents ST HPMA polymers... 

AAm monomer was purchased from Junsei Chemical Co., Japan. DMAEMA monomer, ammonium persulfate (APS), and tetramethylethyl-diamine (TEMED) were purchased from Aldrich. Bovine insulin, N,N-azobis(isobutyronitrile) (AIBN) and glucose oxidase (GOD) were purchased from Sigma Chemical Co. DMAEMA monomer was distilled before use. Other reagents were used as received. 

The most popular thermal initiator is 2, 2 -azobisisobutyronitrile (AIBN), with a half-life (ti/2) of 1 h at 81 °C and 10 h at 65 °C in toluene [8,21]. Generally, 5-10 mol% of initiator is added either all in one portion or by slow addition over a period of time. There are other azo compounds which can be chosen, depending on the reaction conditions. Indeed, the nature of the substituent play an important role as can be seen for 2, 2 -azobis-(4-methoxy)-3,4-dimethyl-valeronitrile (AMVN), with a ti/2 of 1 h at 56 °C and 10 h at 33 °C in toluene. There are also hydrophilic azo compounds, such as 2, 2 -azobis-(2-methylpropionamidine) dihydrochloride (APPH), with a ti/2 of 10 h at 56 °C in water. 

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