Exam. Roll: CURZON-1501Registration No: HA-2639( 2009-10)M.S. SESSION : 2013-14DEPARTMENT OF CHEMISTRYUNIVERSITY OF DHAKA

Physicochemical properties of the binary mixtures of DMSO with methanol , ethanol , n–propanol and n–butanol at different temperatures

Importance of physicochemical properties of binary liquid mixtures

The study of physicochemical properties of binary

liquid mixture provides the way of accumulation of

knowledge about the types of interaction in a binary

mixture of different substances.

It may show the appearance of a new phenomenon,

which is absent in pure state.

The talk is about…Binary Liquid Mixtures

Dissolves both polar and nonpolar compounds and miscible in a wide range of organic solvents as well as water.

As, DMSO is only weakly acidic, it tolerates relatively strong bases.

Because of its high boiling point, 189 °C, DMSO evaporates slowly at normal atmospheric pressure. Samples dissolved in DMSO cannot easily escape compared to other solvents.

Why DMSO?

The hydroxyl group makes the alcohol molecule polar and can form hydrogen bonds to one another and to other compounds. This hydrogen bonding means that alcohols can be used as protic solvent.

Two opposing solubility trends in alcohols are the tendency of the polar OH to promote solubility in water, and the tendency of the carbon chain to resist it.

Why alcohol?

Objective of the researchPreparation of binary liquid mixtures of DMSO with methanol,

ethanol, n–propanol and n–butanol. Determination of density, viscosity, refractive index and dielectric

constant of these binary liquid mixtures over the entire range of composition at five different temperatures.

Determination of interaction parameter, some thermodynamic properties such as free energy of activativation, enthalpy and entropy of activation and excess properties of all those mentioned properties from experimental data over the entire range of composition.

Study of types of intermolecular interactions present in these binary mixtures and the strength of interaction betwen the components.

Comparison of different physicochemical properties of these binary mixtures.

Experimental

Measurement of Density: The densities of the pure components and their binary mixtures were measured with Anton Paar (model DMA 4500) vibrating tube density meter, which is being excited to vibrate at a characteristic frequency. Through a precise determination of this frequency and a mathematical conversion, the density of sample can be measured.

Measurement of Dielectric constant: Dielectric constant was directly measured by ALPHA DCM 470 Dielectric constant meter.

Measurement of Viscosity: The viscosities of the pure

components and their binary mixtures were measured with

Lovis 2000 M/ME Microviscometer which measures

viscosity by rolling ball principle. In the rolling ball

principle, a ball rolls through a closed, liquid-filled capillary,

which is inclined at a defined angle. Three inductive sensors

determine the ball's rolling time between defined marks. The

sample's viscosity is directly proportional to the rolling time.

Measurement of Refractive index: The refractive indices of the pure components and their binary mixtures were measured with Anton Paar (model- Abbemat 300/500) Refractometer. The sample on top of the measuring prism is irradiated from different angles by an LED. At the interface between sample and prism the incident beam is either refracted into the sample or reflected back to into the prism. The reflected beam is detected by a sensor array. From this the critical angle for total reflection is calculated and used to determine the refractive index (RI) of the sample.

Density of the binary systems of DMSO with alcoholsat 298.15 K

Excess density of the binary systems of DMSO with alcohols at 298.15 K

dE =dobs. – dcal dcal. = x1d1 + x2d2

Molar volume of the binary system of DMSO with alcohols at 298.15K

Vmix = ( x1M1 + x2M2 ) / dmix

Excess molar volume of the binary systems of DMSO with alcohols at 298.15K

VmE = Vm - ( x1V1

0 + x2V20 )

Viscosity of the binary systems of DMSO with alcohols at 298.15 K

Excess viscosity of the binary systems of DMSO with alcohols at 298.15K

ηE = ηobs - ηid

Interaction parameter of the binary systems of DMSO with alcohols at 298.15 K

ηid= exp( x1ln η1 + x2ln η2+ x1x2ε)

ε =

21

)ln(lnxx

idobs

Free energy of activation of the binary systems of DMSO with alcohols at 298.15K

ln(η Vm / hN) = -ΔS# / R + ΔH# / RT ΔH# = slope x R ΔS# = - intercept x R ΔG# = ΔH# - TΔS#

Excess free energy of activation of the binary systems of DMSO with alcohols at 298.15K

ΔG#E = ΔG# – (x1 ΔG0# +x2 ΔG0#)

Enthalpy of activation of the binary systems of DMSO with alcohols

Excess enthalpy of activation of the binary systems of DMSO with alcohols

ΔH# E = ΔH# – (x1ΔH#1+x2ΔH#

2)

DMSO + methanol ˃ DMSO + ethanol ˃ DMSO + n-propanol ˃ DMSO + n-butanol

This trend is seemed to be inconsistent with the chain length of the alcohols

Entropy of activation of the binary systems of DMSO with alcohols

Excess Entropy of activation of the binary systems ofDMSO with alcohols

ΔS# E = ΔS# – (x1ΔS# 1+x2ΔS# 2)

Excess entropy is in the order of the binary systems of DMSO with methanol ˃

ethaanol ˃ n-propanol ˃ n-butanol

So, n-butanol + DMSO is the most ordered and n-methanol + DMSO is the least

ordered system in viscous flow

Refractive index of the binary systems of DMSO with alcohols at 298.15K

Excess Refractive index of the binary systems of DMSOWith alcohols at 298.15 K

nE=nobs. –ncal. ncal. = x1n1 +x2n2

Dielectric constant of the binary systems of DMSO with alcohols at 298.15K

Excess Dielectric constant of the binary systems of DMSO with alcohols

εE = ε12 - (ε1X1 + ε2X2) εE = εobserved –εideal

CONCLUSION

Upon addition of alcohols to the DMSO, rupture of H-

bonded structure of these alcohols occurs.

There are mainly non-specific interactions present among

the non-identical components of the systems but in case of

the binary system of methanol and ethanol with DMSO

weak interaction( small magnitude of H-bond) may occur.

Thank you

Supporting Slides