Benzene diazonium salt treatment

Recently, natural fiber has also been treated with benzene diazonium salt to improve its physical, mechanical and thermal properties. Benzene diazonium salt reacted with cellulose in wood and produced 2, 6-diazocellulose by a coupling reaction, as confirmed 

Yields of 2,6-diazo cellulose can be explained as being due to the presence of three hydroxyl groups in the cellulose anhydroglucose unit. One is the primary hydroxyl group at Cg and the other two are secondary hydroxyl groups at and C. The primary 

The same letters are not significantly different at a = 5%. Comparisons were done within the each wood 

Rubberwood, a small difference was found between untreated and its treated samples because of its high density and a little amount of chemical incorporation inside the cell wall [24]. It can be shown from Table 14.2 that the modulus of rupture (MOR) decreased after chemical treatment. 

The lower MOR of treated samples compared to the untreated one is due to the reaction of coupling reagent with cellulose unit in wood yielded azo compound as stated earlier which improved hardness and decreased MOR. This indicates that coupling reaction in wood enhanced brittleness of wood. 

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Among various chemical treatments, alkali treatment with NaOH solution is often chosen to modify cellulose-based materials. Since NaOH reacts with -OH groups of cellulose and reduces hydrophilicity and impurities from cellulose fiber, it improves the compatibility between the cellulose and the polymer matrix. Consequently, significant improvement in the mechanical and morphological properties of composite such as MOE, MOR, compressive modulus, SEM morphology and XRD pattern are observed for the alkali-treated composite materials. Benzene diazonium salt is also an important chemical, which reacts with cellulose in fiber and produces 2,6-diazo cellulose by a coupling reaction. 

In this chapter, various types of chemical treatments including alkali, benzene diazonium salt, o-hydroxybenzene diazonium salt, succinic anhydride, maleic acid, acrylonitrile and nanocaly onto cellulose-based materials will be described and their effect on the structural and mechanical properties of the resultant composites will also be discussed. 

The triazene linker can be used for the immobilization of aromatic diazonium salts, and therefore for aromatic amines, but not for aliphatic amines due to the instability of their diazonium salts. Cleavage of the linker can be achieved under mild acidic conditions to yield the benzylamine resin and the corresponding diazonium salt [136,145,146]. The main difference between the preparation of triazenes in solution and triazenes on solid support is the respective amine, namely bisben-zylamine and polymer-supported benzylamine 114. In solution, it was used in excess to quench unstable diazonium salts and force the reaction to completion. In the solid-phase approach it was immobilized and cannot be used in excess with respect to low loadings. A simple three-step procedure (Scheme 36) starting from benzylamine resin 114 via carboxylate 115 led to the successful preparation of ester resins 116 in essentially higher loadings. Treatment of resin 114 with 4-carboxy-benzene diazonium tetrafluoroborate yielded benzoic acid resin 115. 

Treatment of (153) with a large excess of alcohol yields the diazo ethers (168). Similar products are not obtained in the benzene series. In the presence of low concentrations of acid, (168) condenses with nitrosamines (150) to yield triazines of type (169). The triazines (169) also are readily obtained from the reaction of the diazonium salts (153) with primary... 

There are many variations, and a wide range of aromatic diazonium salts can be used. One method for generating the diazonium salt is treatment of an aromatic amine with nitrous acid (HONO via reaction of HNO3/HCI or NaN02/2 HCl).i62 These diazonium salts can be coupled to other aromatic compounds in the presence of base in what is commonly called the Gomberg-Bachmann reaction. 63 Treatment of 4-bromo-aniline with nitrous acid, for example, gave the diazonium salt (231) which reacted with benzene to give the... 

Aromatic alcohols (phenols) can be prepared by treatment of a diazonium salt (ArN2 ) with water, acid, and heat. In this substitution reaction, water acts as a nucleophile and replaces the excellent nitrogen leaving group (N2) on the diazonium salt. The diazonium salt is prepared in three steps from benzene (or a substituted benzene derivative, but such compounds will be addressed in a later part of this book). First, nitration of benzene with HNO3 and H2SO4... 

The methods described above for alkyl halides (on sp hybridized carbons) cannot be applied to the synthesis of aryl halides (on sp hybridized carbons). The introduction of a halogen to benzene (or a benzene derivative) can be accomplished either by an electrophilic aromatic substitution reaction (Cy FeCls or Br2/FeBr3) or by treatment of a diazonium salt (ArNaO with a halide nucleophile (Cul, CuBr, HBF4, or KI). 

While a cyano group cannot be introduced to a benzene ring by an Sn2 substitution, it can be added by treatment of a diazonium salt (ArN2 ) with... 

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