Diazonium salts derivatizing

The diazonium salt is readily prepared from the aminophenyl group, but does not result from treatment of an aliphatic amine (such as the APTES-derivatized surface) with nitrous acid. The activated surface is now ready for enzyme coupling, since diazonium salts are very reactive toward protein tyrosine residues (Eq. 4.4) ... 

Phenols in trace concentrations were derivatized by coupling with a 4-sulfobenzene-diazonium salt at pH 10.5. The azo dyes were combined with tetradecyldimethylbenzy-lammonium ions at pH 5.0 and, after SPE on a PTFE membrane filter, the end analysis was carried out by RP-HPLC with UVD at 352 nm. LOD was between 40 ppt (phenol) and 2 ppb (2,5-xylenol) for eight phenols tested. The method was used for determination of phenols in river water ... 

Pandurangappa, M., and Ramakrishnappa, T. 2008. Derivatization and characterization of functionalized carbon powder via diazonium salt reduction. Journal of Solid State Electrochemistry 12, 1411-1419. 

MSA is derivatized with a diazonium salt to produce a diazosulfone, which is quantified by HPLC [157]. The flavonoids catechin, epicatechin, 7,8-dihydroxyflavone, and rutin showed a OH scavenging activity 100 to 300 times higher than mannitol, whereas baicalein (5,6,7-trihydroxyflavone), quercetin, myricetin, and morin enhanced the OH production [16]. The pro-oxidant activity of morin increased with an increasing concentration of morin, whereas an increasing concentration of the other three flavonoids did not enhance their pro-oxidant activity. Hanasaki et al. suggested that these pro-oxidant flavonoids produce H2O2 during their auto-oxidation, which then stimulates the Fenton reaction [16]. 

In order to construct an ordered monolayer on a carbon surface, a premodified smooth and functionalized film is needed. Electrochemical reduction of diazonium salts or oxidation of amine-containing compounds and arylacetate produces free radicals, resulting in covalent derivatization of the carbon surface in nonaqueous solutions (Figure 3). The premodification by free radical grafting methods is quite mild, simple, and rapid experimentally. The monolayers prepared as a precursor film for subsequent assembly are stable to harsh environments and can endure elevated temperatures, and especially are organized in order, compact, and charge-rich. 

FIG. 15. Diazonium salt reduction on a boron-doped nanocrystaUine diamond thin-film electrode (A) general reaction mechanism, (B) a series of cyclic vol-tammetric i-E curves in 1 mM 4-nitrophenyldiazonium salt + 0.1 M TBABF4/ CH3CN during the surface derivatization step, and (C) a cyclic voltammetric i-E curve for the derivatized surface in 0.1 M TBABF4/CH3CN. Scan rate = 0.05 V/s. Electrode area = 0.2 cm. ... 

Substrates analogous to (I), (II), and (III) should function with trypsin, pepsin, papain, and other proteolytic enzymes. Furthermore, oxidases could be labeled by this technique with substrates such as hydrazine derivatives that yield diazonium salts on oxidation. Reductases and other enzymes could presumably be derivatized by other suitable substrates and active species. We have recently found that the d form of compound I effectively and fully inhibits chymotrypsin within 15 min when used at a 10/1 ratio to the enzyme. ... 

Spontaneous grafting with DNOj is also possible on silicon. With different types of Si (mono or polycrystalline, highly n or p), the reaction occurs whatever the nature of the substrate, both in the dark and under illumination, with the best yield being obtained with highly doped n polysilicon under illumination [13,71-72]. In the same way, Ge can be spontaneously derivatized with diazonium salts [73-75]. 

Girard, A., F. Geneste, N. Coulon, C. Cardinaud, and T. Mohammed-Brahim. SiGe derivatization by spontaneous reduction of aryl diazonium salts. Appl. Surf. Sci. 282, 2013 146-155. 

Nonetheless, derivatization methods have been successfully employed [56-58,65], most notably via use of the diazonium salt of 4-nitroaniline, For instance, in the study of phenylamide pesticides, no resonance was observed from these colorless compounds however, after derivation to azo dyes, detection limits of (2-4) X 10 M were achieved for monuron, diuron, a-napthylacetamide, and /3-napthylacetamide. Selectivity in distinguishing derivatized products from isomers of monosubstituted phenols (i.e., ortho, meta, and para) has also been shown to be successful, as illustrated in Fig. 8. Moreover, coupling the sensitivity and selectivity of RRS to the well-known spot-test method (qualitatively identifies colorless solutions only by visual identification of the colored products), a more accurate and sensitive characterization method of trace organic compounds is achieved. Such work has been conducted by Nakamura et al. in the characterization and detection of phenols and heterocyclic aromatic compounds on fruit rinds and food preservatives [58]. 

We have found that SWNTs can be functionalized by electrochemical reduction of aryl diazonium salts in their presence. Using this method, about 1 in 20 carbon atoms of the nanotube framework are reacted. We have also found that the SWNTs can be functionalized by direct treatment with aryl diazonium tetrafluoroborate salts in solution, or by in situ generation of the diazonium moiety using an alkyl nitrite reagent. These functional groups give us handles with which we can direct further, more selective derivatization (Figure 5.2) and we recently reviewed the area of covalent sidewall derivatization of SWNTs. 

Basic studies on diazonium-CNT chemistry led to two very efficient techniques for SWCNT derivatization solvent-free functionalization [176] and functionalization of individual (unbundled) nanotubes [175], With the solvent-free functionalization (Scheme 1.26), heavily functionalized and soluble material is obtained and the nanotubes disperse in polymer more efficiently than pristine SWCNTs [176], With the second method, aryldiazonium salts react efficiently with the individual (unbundled) HiPCO produced and sodium dodecyl sulfate (SDS)-coated SWCNTs in water. The resulting functionalized tubes (one addend in nine tube carbons) remained unbundled throughout their entire lengths and were incapable of reroping. [175],... 

Although UV is the most widely used detection technique found for the analysis of the major opium alkaloids in different matrices, another optical detection techniques have been found. Luminescence is also a very attractive detection system, due to its low sensitivity but it has been scarcely employed in the analysis of the major opium alkaloids of samples of forensic interest. FLD have been employed for the analysis of a binary mixture of MO and 6-AM based on the derivatization with diazomium salt of aniline at 0°C [121]. It was necessary to optimize all the conditions that affect derivatization (diazonium concentration and reaction time) and those related with the separation (electrolyte concentration, pH, p-CD concentration, organic additives, and separation potential) but good linearity was obtained in the range of 50-2000 ng/mL. 

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