**6. The authors concluded**


#### **6.1 Current applications of the Fenton oxidants**

The Fenton Oxidants (HO•, Fe = O+2, and Fe = O+3) are being investigated as molecular scissors for insertion of reactive functional groups into otherwise inert substrates, such as carbohydrates. Oxidation of hydroxyl groups to carbonyl or carboxylic acid groups will allow them to act as carriers for various molecules with ramification in many sectors.

### *6.1.1 Hydroxyl radical oxidation of carbohydrates*

Neyra et al. (2014, 2015) used a catalytic amount Fe+2 ions to produce HO• radicals from H2O2 to oxidize hydroxyl groups of acetylneuraminic acid monomers (2014) and tetramers (2015) to carbonyl and/or carboxylic groups. The goal of the experiment was to modify the sugars to create anchors for proteins so as to create vaccine adjuvant platforms [120, 121].

#### *6.1.2 Perferryl-oxo oxidations of carbohydrates*

Sorokin et al. (2004), using 'heme'-chelated Fe+3 ions, oxidized glucose monomers in starch fibers at C2 and C3 to produce acid / aldehyde pairs without hydrolyzing the flanking glycosidic bridges. The dual oxidations allow for two independent modifications of the glucose monomers in the starch chain [122–124].

#### *6.1.3 Ozone-Fenton systems*

Ozone (O3) is being considered as an alternative to H2O2. Ozone gas can be activated by UV (O3!O2 + •O•) to produce oxygen radicals, or by reaction with iron

#### *A History of the Fenton Reactions (Fenton Chemistry for Beginners) DOI: http://dx.doi.org/10.5772/intechopen.99846*

ions (Fe+2, Fe+3 + O<sup>3</sup> !Fe = O+2, Fe = O3+ + O2, thus producing each Fenton oxidant without water as a byproduct.

Pestovsky (2004, 2005, 2006) reacted Fe+2 ion with O3 in aqueous buffer as an alternative method of creating (Fe = O)+2 ion. The signature of HO• radicals: 1 e� oxidations, were not detected for the oxidation of several classes of organic molecules [125–127].

Bataineh (2015a), and Bataineh et al. (2012, 2015b) compared the oxidation of DMSO with Fe+2 and O3 in aqueous phosphate vs. acetonitrile solvents. In acetonitrile the primary product was DMSO2, an oxygen addition reaction. In buffered H2O, ethane and methylsulfinate were the primary products, indicating fragmentation of DMSO occurred by HO• oxidation [128–130].

Enami et al. (2014) fired microjets of aqueous FeCl2 into sprays of either O2 or O3/ O2 mixed gases. Particles detected by negative ion MS proved that Fe+2 and O3 produces new particles not seen in FeCl2 or FeCl2/O2 sprays [131].

#### *6.1.4 Fenton systems for bioremediation*

Fenton oxidants are gaining popularity as agents of bioremediation because of their ability to mineralize toxic organic molecules without contamination by ecologically damaging elements (halogens, heavy metal ions, etc.).

*6.1.4.1 Ozone (O3) for bioremediation with (HO•) radical or (Fe = O)+3 ion*

Turan-Ertas & Gurol (2002) compared ozone (O3) against Fe+3/H2O2 in the degradation of diethylene glycol [(HO-CH2-CH2)O], a toxic byproduct of the synthesis of ethylene glycol. The authors compared the diethylene glycol oxidation profile by O3 and Fe+3/H2O2. Both procedures were effective in degrading diethylene glycol, however the Fe+3/H2O2 oxidation produced fewer and simpler products [132].
