Review on kinetic studies of α‑hydroxy acids (glycolic, mandelic, citric, tartaric and malic) and some other organic compounds with water soluble nano particles of colloidal MnO 2 in absence and presence of non‑ionic surfactant (TX‑100)

This review paper deals with the kinetic studies of α-hydroxy acids (glycolic, mandelic, citric, tartaric, and malic) and some other organic compounds with water soluble nano particles of colloidal MnO 2 in the aqueous and micellar media i.e., non- ionic surfactant (TX-100). The reaction has both non-autocatalytic and autocatalytic paths. Both in the absence and presence of non-ionic surfactant i.e., Triton X-100, first-order rate with respect to colloidal MnO 2 and α-hydroxy acids is observed. Non-ionic surfactant (Triton X-100) catalyses the reaction due to multiple hydrogen bonding (intermolecular hydrogen bonding) whereas cationic CTAB (cetyl trimethyl ammonium bromide) and SDS (sodium dodecyl sulphate) show no effect.


Introduction
The origin of charge on colloidal particles (nano particles) has not been completely understood. However, it has been seen that colloidal sols are constantly connected with minute amounts of electrolytes and that, assuming the last option are totally eliminated by relentless dialysis, the sols become shaky. It is accepted, hence, that the charge on the colloidal particles is because of particular adsorption of one or the other positive or negative particles on a superficial level. One more conceivable manner by which colloidal particles might get charge is by direct ionization of the material comprising the particles. Today is the era of nanotechnology. Nanoparticles are used in many ways [1][2][3][4][5][6][7][8]. The adsorption of surfactants onto colloidal particles is normally connected with enhance diffused stability.
Special cases to this general perception can of obviously happen with the inversion of the polarity of the particles charge, notwithstanding the adsorbed non-ionic [9] surfactant like TX-100 or Tween-80 etc. TEM microstructure of colloidal manganese dioxide indicates the shape and nature [10]. The use of colloidal solutions (especially for colloidal MnO 2 ) has been quite fruitful to concentrate on quick interfacial cycles [11]. Subsequent upon delineation, soluble manganese dioxide-natural corrosive responses have likewise been worked to determine the thermodynamic parameters [12][13][14][15] with the help of Arrhenius and Eyring equations. In explaining the effect of surfactants on the above redox reactions, adsorption was considered as the first step. However, it needs in-depth study consideration. Therefore, the present proposal review has been presented to obtain more knowledge on colloidal MnO 2 , 1 3 80 α-hydroxy acids, some other organic compounds, and surfactants.
KMnO 4 has been used as a strong oxidant. A lot of stages of the oxidations by KMnO 4 involved during the course of chemical reactions. MnO 2 , normal form of manganese is a brown insoluble material. A few forms can exist, and the end product of permanganate oxidation produces MnO 2 except in strongly alkaline solution where its stable enough to be the terminal stage and in certain oxidations in acid solution. A neutral solution containing a yellow brown manganese (IV) species, attributed to H 2 MnO 4 2− , has been found to follow the Beer-Lambert law.
The use of MnO 2 has been a little bit limited. In doing kinetics experiments one more limitation is forced the manganese dioxide being available as powder, intermediates framed at the strong/arrangement interface can't be eliminated in that frame of mind, notwithstanding the way that their existence is gathered from the rate estimations. Perez-Benito and his co-workers [16] have detailed the water soluble MnO 2 (nano particles). The soluble form colloidal MnO 2 was prepared by action of KMnO 4 and Na 2 S 2 O 3 under neutral conditions. The colloidal solution so obtained remained stable for several weeks and perfectly dark brown.
The utilization of colloidal arrangements has been effective to concentrate on quick interfacial cycles [17]. Subsequent upon delineation, soluble manganese dioxide (nano particles)-natural corrosive responses have likewise been worked to determine the thermodynamic parameters . Still, the effects of surfactants of nano sized MnO 2 have not been designed in more detailed. This review deals with the kinetic studies of α-hydroxy acids (glycolic, mandelic, citric, tartaric, and malic) and some other organic compounds with water soluble nano particles of colloidal MnO 2 in the aqueous and micellar media i.e., non-ionic surfactant (TX-100).
The following reaction can take place which is as: The above prepared colloidal solution was dark brown and stable for several weeks.

Kinetic study
Experiments were done at constant temperatures in water-bath, which was designed and assembled. A mixture containing appropriate amounts of all the reactants (except oxidant) was prepared. In the water-bath the resulting arrangement was passed on to 30 min to obtain equilibrium. With Bausch & Lomb Spectronic-20 spectrophotometer, the development of the response was observed spectrophotometrically through following vanishing of water soluble colloidal MnO 2 at λ max (wavelength 390 nm) (Fig. 1). By keeping the concentration of α-hydroxy acids (glycolic, mandelic, citric, tartaric, and malic) and some other organic compounds in excess pseudo-first-order conditions were carried on and λ max at 390 nm. Values of the pseudo-first-order rate constants were evaluated from the slopes.

Reactions in aqueous medium
The kinetic investigations of α-hydroxy acids and some other organic compounds were carried out spectrophotometrically at wavelength 390 nm (λ 390 [20][21][22][23][24][26][27][28][29][30] at different reaction conditions. As the concentration of MnO 2 increases the values of both k obs1 and k obs2 decrease. These results are against the norms of kinetics. Such type of behavior may be due to flocculation of the colloidal particles of MnO 2 . In numerous oxidation responses of organic compounds by permanganate [31,32] such report has earlier been observed. If gum arabic (a protective colloid) is present, a competition between the gum Arabic and reductant (α-hydroxy acids). Gum arabic and the -OH groups of reductants (α-hydroxy acids) are liable for the adsorption on the outer layer of the nano sized MnO 2 .

Reactions in presence of cationic, anionic and non-ionic surfactant
To observe the effect of cationic, anionic, or non-ionic surfactant under different conditions to perform the reactions i.e., CTAB + reaction mixture (α-hydroxy organic acids + MnO 2 + HClO 4 ), SDS + reaction mixture (α-hydroxy   82 organic acids + MnO 2 + HClO 4 ), and TX-100 + reaction mixture (α-hydroxy organic acids + MnO 2 + HClO 4 ). Initial observations showed that CTAB + reaction mixture (α-hydroxy organic acids + MnO 2 + HClO 4 ) and with some other organic compounds, became turbid. CTAB micelles have positive charge while colloidal MnO 2 has negative charge [16,18,32,33] on their surface. Sodium dodecyl sulphate (anionic surfactant) neither catalyzed nor inhibited reactions. Due to negative charge on their head group will repel MnO 2 due to negative charge. The effect of non-ionic surfactant with α-hydroxy organic acids by MnO 2 were studied at fix concentration of reductant, MnO 2 and temperature at 30 °C and with some other organic compounds were also studied in the same manner but different reaction conditions.
To observe the effects of [reductant, α-hydroxy organic acids] and with some other organic compounds, [oxidant, colloidal MnO 2 ], [HC1O 4 ] and temperature in aqueous medium and in micellar media i.e., TX-100 at fixed concentration. We can see that a similar design is being followed as respects the variations in [MnO 2 ], [α-hydroxy organic acids], and also with some other organic compounds and [ HC1O 4 ]. The impact of shifting temperature on the rate was likewise something similar i.e., increased with increase in temperature. The effect of [TX-100] are synergist up to specific concentration and afterward stayed steady (besides in the event of malic and citric acids).

Effect of TX-100
Adsorption is a surface phenomenon which occurs at the surface [34]. Surface chemistry deals with systems where surface effects are important. Surface effects are of tremendous biological and industrial significance. It is well known that the effects of TX-100 (catalytic) and gum Arabic had an inhibitory. Therefore, the adsorption isn't the main variable capable to make to the catalytic role with non-ionic surfactant on α-hydroxy acids and nano sized MnO 2 . There are other factors such as hydrogen bonding, interfacial water properties, etc., can also not be eliminated.
The hydrogen bonding between the above surfactant (TX-100) (Fig. 2) (structure of TX-100) and reactants plays a significant role. In α-hydroxy acids (glycolic, mandelic, citric, tartaric, and malic) which contain OH and COOH groups. Hydrogen bonding may play very important role to these groups and also with some other organic compounds. Thus, surfactant helps to bring the reactant molecules closer and closer and be responsible for facilitating the reaction. In case of Tween-80 with citric acid rate is much higher than TX-100 due to different OH multiple bond in Tween-80 [35].

Conclusion
The review done on the kinetic study of α-hydroxy organic acids and also with some other organic compounds by colloidal MnO 2, and the role of TritonX-100 have been described interestingly. The response happens through the adsorption of α-hydroxy organic acids and with some other organic compounds on the outer layer of the colloidal MnO 2 particles. It was affirmed that gum arabic and TritonX-100 meaningfully affected the response rate. 83 The reactant impact of TritonX-100 might be because of H-holding between the TritonX-100 also reactants (MnO 2 , α-hydroxy organic acids and with some other organic compounds). Surfactant helps to bring the reactant molecules closer and closer and be responsible for facilitating the reaction.