Protic ILsILs can be divided into two broad categories, viz., aprotic ionic liquids (AILs) and protic ionic liquids (PILs)

PILs are formed through the transfer of a proton from a brӧnsted acid to a brӧnsted base

Commonly used cations are 1°, 2°, 3° ammonium, imidazolium, pyrrolidonium, caprolactum, glycine, proline etc & anions are carboxylate, nitrate, TFSI, BETI, Tfa, SCN- , HSO4

-etc

General propertiesThe choice of the cation and anion determines the physicochemical properties.

A key feature of PILs is that they are capable of hydrogen bonding, including proton acceptance and proton donation

The majority PILs have nonnegligible vapor pressures, but their beneficial properties for the applications out weigh this potentially negative property[1]

[1]Greaves,T.L; Weerawardena,A; Fong,C;Krodkiewska,I; Drummond,J, J. Phys. Chem. B 2006, 110, 22479-22487

PreparationAcids are added slowly to bases in a stoichiometric ratio with vigorous stirring

CH3CH2NH2 + HNO3 CH3CH2NH3+ NO3-

As neutralization reaction is exothermic a low Temperature should be maintained to prevent evaporation of base

short chain carboxylic acids (formic, acetic) are prone to degradation with the formation of amide as byproducts

Physico chemical propertiesGlass Transition:

The glass transition is indicative of the cohesive energy

within the salt, it is decreased by repulsive Pauli forces from the overlap of closed e¯ shells and increased through the attractive Coulomb and vanderWaals interactions[2]

It is measured by DSC

[2] Xu, W.; Cooper, E. I.; Angell, C. A. J. Phys. Chem. B 2003, 107,6170.

Melting Point & Thermal StabilityFor low mp PILs, sufficient steric hindrance needed to disrupt the packing efficiency and minimize the hydrogen bonding.

PILs with a large proton-transfer energy will decompose before reaching their boiling point[3]. The decomposition temperatures(Td) of the PILs lie mostly between 120⁰ and 360 °C.

Td is measured by DSC

[3]Belieres, J.-P.; Angell, C. A. J. Phys. Chem. B 2007, 111, 4926

DensityThe density decreases slowly as the alkyl chain

length increases for alkyl ammonium cations, alkylimidazolium cations, or alkylcarboxylate anions

The substitution of a OH¯ group onto the alkyl chain of either of the ion increased the density, probably because of increased H- bonding decreases the ion-ion separations[4]

It is measured by density meter(Anton Paar)

[4]Greaves, T. L.; Weerawardena, A.; Fong, C.; Krodkiewska, I.;Drummond, C. J. J. Phys. Chem. B 2006, 110, 22479

Refractive Index & Surface tensionThe refractive index (nD ) of a material is a measure of polarity

The surface tension(σ) will be decreased when the ions have a higher packing efficiency

Substituting a OH¯group onto either of the ion increased the σ & nD

increasing the alkyl chain decreases σ while increases nD

[5]

σ is measured by du nouy method among others[5]Greaves, T. L.; Weerawardena, A.; Fong, C.; Krodkiewska, I.;Drummond, C. J. J. Phys. Chem. B 2006, 110, 22479.

Ionic conductivityThe ionic conductivity is governed by the mobility of the ions. It depends on the viscosity and the number of charge carriers

It also depend on the molecular weight, density, and ion sizes

Any ion association will cause a decrease in the ionic conductivity through decreasing the number of available diffusible ions[6]

It is measured by conductivity meter(solartron)

[6]Tokuda, H.; Hayamizu, K.; Ishii, K.; Susan, M. A. B. H.; Watanabe,M. J. Phys. Chem. B 2004, 108, 16593

ViscosityThe viscosity is dependent on the ion-ion interactions, such as vander Waals interactions and hydrogen bonding

The anion structure has a far greater effect on the viscosity than similar changes to the cation[7]

It is measured with a Carri-Med CSL2 100 Rheometer

[7]Chemical Reviews, 2008, Vol. 108, No. 1

Application of PILsPILs are used in organic synthesis as a solvent

as well as catalyst

It is used as nonaqueous electrolyte in polymer membrane fuel cells

It also act as lubricants

It has many industrial & biological application

It can also be used as a stationary phase in GC

Our plan: what to doOur intend is to prepare ammonium based PIL because

It is less toxic

It can be used as a CO2 scavenger in industrial process

So our proposed base will be N,N-diethyl hydroxyl amine(BP:124-126)

The hydroxyl group present will influence for hydrogen bonding

High thermal decomposition temperature

Among acids the inorganic anions are more likely to be solid at room temperature[8] & also they are very much aggressive

Formic & ethanoic acids are also not suitable for distillation because of low thermal stability

So we proposed a strong carboxylic acid CF3COOH

which enhances the proton transfer process

[8] Tamar L. Greaves etal, J. Phys. Chem. B 2006, 110, 22479-22487

Detailed processWater content should be removed from starting material with the help of molecular sieve(4A°)

Equimolar acid will be taken & then added to the base drop wise to prevent the formation of amide

The system should be kept in ice bath during acid addition & then with constant stirring(at room temp.) near about 24 hrs

The product is then characterized by 1H NMR(δ≈3) & FT-IR(broad peak:3500-2400 cm-1)

Detailed processThe PILs obtained will be dried under high vacuum (.1pa) for over night to remove excess water content

The water content will then be determined by karl-fischer titrator(DL39-mettler toledo)

The various thermo physical properties like Tg, Tm, Tb, ρ, η, k, cp, nD etc can be measured at various ranges of temperature by using the above mentioned technique

Binary mixtureThe binary mixture will be made with water, aceto nitrile & methanol with different mole fraction of PILs

Apart from several usefulness of binary mixture it lowers the energy requirements for CO2 absorption

Molar excess volume, deviation in viscosity, heat capacity etc will be calculated

The values are then fitted to Redlich-Kister[9]

polynomial equation to determine the binary coefficients to know the molecular interaction

[9] Kiki A. Kurnia · M.I. Abdul Mutalib · T. Murugesan ·B. Ariwahjoedi,J Solution Chem, 2011, 40, 818–831