1 Introduction

Organic compounds contain mainly carbon, and hydrogen as the backbone of the structure. It also consist some other elements, i.e. oxygen, nitrogen, sulphur etc. and its oxidation are carried out by either addition of oxygen or loss of electron. It includes remediation of pollutants or combustion process. Nowadays, study of oxidation of organic compounds present in environment is of immense importance and there are several oxidants reported for degradation processes [1,2,3]. With the passage of time, detailed study of the kinetics and mechanism of redox reaction has draw much attention, and mechanisms of various oxidation reactions have been neatly explained [4, 5]. Among various oxidants, N-halocompounds broadly used as powerful oxidizing agent in both catalyzed [6,7,8], and un-catalyzed reactions [9,10,11]. These are also the source of halogen and act as halogenating agent [12]. It has great properties sometimes it behaves like a base, nucleophile, hypohalite species etc. [13, 14].

Oxidation of ketones [15, 16], d-arabinose and mannose [17], reducing sugar [18] by NBA were reported. While, Singh et al. [19] reported that the reaction followed fractional order dependence on [NBA], first order on [Ru(III)], zero order on [glycerol and glycol] and positive effect of [H+] was observed. Mathiyalagan and Sridharan [20] studied the kinetics of oxidation of benzyl ether by NBS. The reaction followed first order kinetics with respect to both [NBS] and [benzyl ether]. There are several reports also available in the literature on the oxidation of organic compound by NBS [21, 22]. Gowda et al. studied the oxidation of hydrophobic tetrapeptide [TP] sequences of elastin. The reaction was followed identical kinetics, first order each in [NBS], [AA] and [TP], no effect on the rate of [H+] was observed [23]. Tiwari et al. [24] studied the kinetics and mechanism of the oxidation of Gly by NBS. Reaction followed first order kinetics on both [NBS] and [Gly] and inverse first order on [H+].

Oxidation of different organic compounds by N-chlorobenzenesulphonamide [25], bromate [26], diperiodatonickelate [27], have been also reported. NBP is also among one of N-haloimides, as an oxidizing compound.

2 Synthesis of NBP

Initial molecule for the synthesis of NBP is phthalimide, (7.36 g, 50.0 mmol, 1.0 eq), Na2CO3 (3.98 g, 37.6 mmol, 0.75 eq), and KBr (5.95 g, 50.0 mmol, 1.0 eq) were mixed in a 500 ml round bottom flask followed by addition of doubly distilled water (200 ml). Then flask was cooled on an ice water bath for 10 min, afterward potassium peroxymonosulfate (30.8 g, 50.1 mmol, 1.0 eq) drape in 75 ml water, with an intense stirring (700 rpm), for 10 min. Next the addition of the oxidant resulted in intense liberation of bromine gas, and thus the flask was capped with a glass stopper between additions. The mixture rapidly turned into an orange lather suspension with visible bromine gas above it. The suspension was kept for continuous 24 h stirring, at which point it had become a yellow solution with a white precipitate. Stirring was continued another 24 h, until the solution above the precipitate was almost clear. The suspension was filtered on a Büchner-funnel and the filter cake sucked dry for a period of 30 min. The white precipitate was dissolved in boiling toluene (150 ml), hot filtered into a beaker and left to cool slowly to ambient temperature, covered with an aluminum foil. Lastly, upon reaching ambient temperature, precipitation had begun and the beaker was placed in a refrigerator at 4 °C for a period of 17 h, before filtering the precipitate on a Buchner-funnel. The filter cake was washed with n-pentane (30 ml) to give 6.52 g (57%) of small white crystals. The mother liquor was concentrated, filtered and the filter cake washed with toluene, and n-pentane. And it was grind with mortar to obtain fine powder of NBP [28].

3 Properties of NBP

  1. (a)

    It is turbulent in front of sun light but stable when placed in dark. Because it shows photochemical activity and get auto degrade in the presence of light [29].

  2. (b)

    It is sparingly soluble in water but easily soluble in organic solvent i.e. acetic acid, acetonitrile etc. [30].

  3. (c)

    After oxidation it generally oxidized into phthalimide which is non-toxic compound and sometime its reaction with organic compounds give carbonyl and cyanide compounds [31, 32].

  4. (d)

    It contains very polar N–Br bond, so it easily relieve bromine ion for bromination [33] (Fig. 1).

    Fig. 1
    figure 1

    Structure of N-bromophthalimide

    Full size image
  5. (e)

    It has different oxidizing species in acidic and basic medium, so it oxidized various organic compounds [34, 35].

4 Reactive species of NBP

N-bromophthalimide was known as powerful oxidizing, and brominating agent. There are five possible reactive species of NBP is reported i.e. free NBP, protonated NBP, Br+, HOBr, (H2OBr)+ [82,83,84,85], as per the following equilibria:

$${\text{NBP}} + {\text{H}}_{2} {\text{O}} \rightleftharpoons {\text{HOBr}} + {\text{NHP}}$$
(1)
$${\text{NBP}} + {\text{H}}^{ + } \rightleftharpoons {\text{NHP}} + {\text{Br}}^{ + }$$
(2)
$${\text{NBP}} + {\text{H}}^{ + } \rightleftharpoons ({\text{NBPH)}}^{ + }$$
(3)
$${\text{HOBr}} + {\text{H}}^{ + } \rightleftharpoons \left( {{\text{H}}_{2} {\text{OBr}}} \right)^{ + }$$
(4)

Selection of reactive species of NBP was mainly depend on kinetic behavior of medium (acid/base), and phthalimide. Reactive species, leads to a rate law capable of explaining all the kinetics observations and other effects. If phthalimide only showed negative effect on reaction kinetics then HOBr will be possible reactive species (Eq. 1). And acid (H+) shows first order and phthalimide has negative effect, than possible reactive species for the reaction will be Br+ (Eq. 2). If phthalimide did not show any effect and acid followed positive fractional order then NBP or protonated NBP will be reactive species for the oxidation process (Eqs. 3, 4).

5 Overview of earlier work done

NBP has very polar N–Br bond which easily relive bromine for bromination reaction and easily oxidized organic compounds, it is unstable in the presence of sunlight. Researcher managed to set oxidation of organic compounds brick by brick and crafting a formidable pathway from un-catalyzed to catalyzed (transition metal ions and surfactants) oxidation process, and we summarize all report below.

5.1 Oxidation of organic compounds by NBP (uncatalyzed)

As we already know that un-catalyzed reaction required more activation energy to react together. Various reports available in literature for un-catalyzed oxidation of organic compound [36, 37]. It needs more time and energy to complete the reaction, so ultimately increases the cost of the reactions. We found only few reports for oxidation of organic compounds by NBP, e.g. Benzhydrols [38], aspirin [39], substituted oxo-butonic acids [40] in acidic medium.

5.2 Oxidation of organic compounds by NBP (surfactant catalyzed)

Surfactants act as catalyst by making micelles when dissolved in water [41]. It aggregates above certain concentration called critical micelle concentration (CMC) to form micelles. And shapes of micelles i.e. rod like, spherical, bi-layers, reverse are responsible for its catalytic activity. Each surfactant has its specific CMC value i.e. CTAB = 8 × 10−4 mol/l, SDS = 8 × 10−3 mol/l. It has both hydrophobic and hydrophilic portion. The rate of reaction has been altered by adding surfactants; it can either increase or decrease the rate of reaction. There are two types of surfactants i.e. cationic and anionic. So, micellar catalyzed reactions have evinced prodigious interest because of their application in many industrial processes. It has some other application like wetting agents, solubilizers, preservatives etc. Normally catalytic activity of the substances is depends on its reaction with substrate, nature of oxidant and conditions (Table 1). Various literature available for micellar catalyzed oxidation of organic compounds with different oxidant, such as chloramines-T, NBS, NBP etc. [42,43,44].

Table 1 Surfactants catalyzed oxidation of organic compounds by NBP
Full size table

5.3 Oxidation of organic compound by NBP (transition metal ions catalyzed)

As we all know that transition metal ions have incompletely filled d-orbital, and it easily form one or more stable ions. And have variable oxidation state. As catalyst mainly platinum group among transition metal ions are selected i.e. ruthenium(III), iridium(III), palladium(II) etc. [70]. It is the key material for various industrial processes and can be recycled with less energy and time [71,72,73,74,75]. By literature, we found several articles on the oxidation of several organic compounds NBP in transition metal catalyzed system in acidic and alkaline medium, i.e., d-glucose [76, 77], d-fructose [78], glycine [79, 80], valine [81,82,83], β-alanine [84], leucine [85], d-arabinose [86].

Overall, it can be said that oxidation efficiency of NBP can be increased up by the used up of catalyst. And from above table, it is very clearly understand that N-bromophthalimide is act as active oxidant for the oxidation of organic–inorganic compounds, but still this needs more attention to use as an oxidant. In light of the available information, and of our continued interest in the chemistry of N-bromophthalimide, the potential applications of these compounds still remain largely untouched as evident by the scant information available in the literature.

6 Factors affecting oxidation of organic compounds by NBP

6.1 Temperature

The rate of a reaction always increases on increasing temperature, irrespective of the reaction being endothermic or exothermic, because of an increase in the number of activated molecules. In general, the rate of a reaction is doubled on increase in temperature by ten degrees. An examination of the rate expression in the form

$${\text{Reaction}}\;{\text{rate}} = {\text{Rate}}\;{\text{constant}} \times \left( {{\text{Reactant}}\;{\text{concentration}}} \right)^{\text{order}}$$

It shows that the rate constant is a temperature dependent term, but reactants concentrations and the reaction order are eventually not affected by temperature. Thus, rate constant is independent of reactant concentration, it varies with temperature. The activation energy for a reaction is experimentally determined through the Arrehenius equation and Eyring equation.

6.2 Catalyst

Activating effect of certain substance exert a special catalytic force upon the reactants, but in simple manner, catalysis is the process in which alter the rate of a chemical reaction is increased by means of a chemical substances known as a catalyst or a substance that modifies the transition state to lower the activation energy. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed. Thus, the catalyst may participate in multiple chemical transformations, although in practice, catalysts are sometimes consumed in secondary processes. The catalyst increases rate of reaction by providing a different reaction mechanism to occur with lower activation energy. But sometime it decreased the rate of reaction. In present review transition metal ions and surfactants (CTAB, SDS) were use as catalyst, where anionic surfactants sometime retard the rate of reaction.

6.3 Ionic strength

The ionic strength (I), refer to the strength of electric field in the solution according to the theory of Bronsted and Bjerrum [87], which postulates the reaction through the formation of an activated complex. According to this theory, the effect of ionic strength on the rate for a reaction involving two ions:

$$\log {\text{k}} = \log {\text{k}}_{0} + 1.02\;{\text{Z}}_{\rm A} {\text{Z}}_{\rm B} {\text{I}}^{1/2} .$$

where ZA and ZB are the valency of the ions A and B, k and k0 are the rate constant in the presence and absence of the added electrolyte respectively. A plot of log k against I1/2 should be linear with a slope of 1.02 ZAZB. If ZAZB have similar signs, the quantity ZAZB are positive, and the rate increases with the ionic strength having positive slope, while if the ions have dissimilar charges, the quantity ZAZB are negative and the rate would decrease with increase in ionic strength, having negative slope.

6.4 Effect of dielectric constant

For the study of dielectric constant of the medium, various solvent i.e. acetic acid and acetonitrile etc. were generally used in different percentage (%). The effect of dielectric constant of the medium on the rate constant of a reaction between two ions has been described by the well known equation given below

$$\log {\text{k}} = \log {\text{k}}_{0} - \frac{{{\text{Z}}_{\rm A} {\text{Z}}_{\rm B} {\text{e}}^{2} {\text{N}}}}{{2.303(4\uppi \upvarepsilon ){\text{d}}_{\rm AB} {\text{RT}}}} \times \, \frac{1}{\text{D}}$$

where k0 is the rate constant in a medium of infinite dielectric constant, ZA and ZB are the charges of reacting ion, dAB refers to the size of activated complex, T is absolute temperature and D is dielectric constant of the medium. This equation shows that if a plot is made between log k versus 1/D, a straight line and—ZAZB and e2N/2.303(4πЄo)dABRT will be equal to slope. And with help of this equation we can also calculate the size of activated complex (dAB).

7 Economics of the process

After oxidation of organic compounds, NBP gave phthalimide, carbonyl compound, which is non-toxic and after separation we can use it for another reaction. And it is environment favorable compound. If we used NBP in proper manner with precaution and by using catalyst we can decrease cost of reaction. And from above study we saw that these reactions did not required any type of costly instruments or chemicals. But still it need more focus because it’s reported literature, available only in laboratory scale or pilot scale not for industrial purpose.

8 Conclusion

Use of NBP, as an oxidant is still field of experiment; we need more, to focus on its diverse behavior. In summary, N-bromophthalimide was successfully used to oxidize kinetically various organic compounds either catalyzed (micellar or transition metal) or un-catalyzed reaction. Mainly two experimental methods were use for the degradation process i.e. iodometric, and potentiometric. In present review catalyst with different active species gave various reactive species of NBP to oxidize various organic compounds. And NBP is unstable for more than 24 h, so we have to develop a method for its stability for long time. Thus, NBP could be used as promising oxidant for the oxidation of pollutants present in water.