Rate of Isomerism of [Co(en)2Cl2] Essay

In the course of this experimentation the graze of isomerism for the coordination heterogeneous cisCo(en)2Cl2Cl was refractory using UV/Vis spectrometry. Using a range of wavelengths the optimum spectrometer setting for psychoanalysis was identified. The corresponding maximum and momentimum absorbance of the cis and trans isomers respectively at 540 nm meant that it was selected as the wavelength to teach the rate of conversion among the isomers. The first order rate invariable was calculate to be 0.0092 m-1 which is somewhat similar to the belles-lettres note value of 0.00845 m-1 (Brasted and Hiriyama 1958). The half life (t 1/2) was found to be 75.34 minutes.IntroductionThe compound Co(en)2Cl2+ is cognise as a coordination complex, that is, it consists of a Cobalt atom surrounded by an array of molecules to which it is bound, called ligands (Brown 2010). In this case the ligands are Ethylenediamine which are bidentate, kernel bound in twain locations. These ligands are bonded between the two atomic number 7 atoms as seen in infix 1 below. This complex occurs in two geometric isomers, cis-Co(en)2Cl2 + and trans-Co(en)2Cl2 +. In this experiment the Chloride salt form of the complexes were apply i.e. cis-Co(en)2Cl2Cl. find 1The Trans and Cis isomers of Co(en)2Cl2+Source Shapter ,J. 2014 Experiment 1 Rate of Isomerism cisCo(en)2Cl2Cl, Flinders University, Australia The Cis- isomer form of the complex which is purple in solution reacts to form the Trans- isomer which is green in solution. This experiment uses spectroscopy to quantify the conversion of the Cis into the Trans isomer due to the incident that the concentration of the Cis isomer is comparative to the conflict in absorbance of the two complexes in solution. This isomerism of the Cis-form is a first order reaction and its rate is expressed in equation 1 below. comparability 1By measuring the optical densities at time 0, t and infinity the rate unbroken k can be repaird with equa tion 2, a rearranged and substituted form of the formula utilise above. Equation 2a)Which rearranges to giveb)ExperimentalSolutions of 2 10-3 M Cis- and Trans-Co(en)2Cl2Cl were prepared and placed in hoi polloitric flasks of 100 ml and 10ml volumes respectively. Samples of these solutions were placed in cuvettes and metric in a spectrometer over the range of wavelengths between 350 and 700 nm. The Varian Car 50 UV-Vis spectrometer recorded the absorbance of the two isomers and produced a print out which was used to identify the correct wavelength for further spectroscopy (see Appendix 1). Using the SP 880 Metertech spectrometer, the absorbance was measurable and recorded as seen in Table 1. Next the Cis isomer solution was change in a water bath at 40 degrees Celsius and a sample was taken and cooled in an ice bath. The absorbance of the sample was then measured using the wavelength previously selected. This was repeated at ten minute intervals for an hour. in conclusion a l ast sample of the cisCo(en)2Cl2Cl was analysed with the spectrometer 24 hours after to restrict the value.ResultsTable 1 Absorption of the Two Isomers at Various Wavelengths Wavelength (nm)CisTrans3500.4680.1443600.2890.0903700.2070.0873800.1800.0913900.1700.091 cd0.4660.3974100.1230.0704200.0920.0574300.0660.0494400.0490.0474500.0410.0484600.0430.0484700.0490.0454800.0610.0394900.0760.031Wavelength (nm)CisTrans5000.0930.0255100.1100.0205200.1240.0175300.1340.0175400.1370.0205500.1340.0255600.1290.0345700.1220.0445800.1160.0555900.0650.1096000.1020.0716100.0950.0756200.0850.0746300.0730.0676400.0600.0556500.0490.0496600.0350.0386700.0260.0286800.0180.0206900.0130.0137000.0090.008Figure 1 Absorbance against Wavelength of Cis and Trans IsomersTable 2 Absorbance of Cis Isomer at 540 nmTime (min)Cis AbslnDt-Dy = -0.01104 X 2.40936100.117-2.51331-2.519758607200.108-2.63109-2.630158414300.100-2.74887-2.74055822400.093-2.8647-2.850958026500.089-2.93746-2.961357833600.082-3.07911-3.071757 639t 0.036Figure 2 Natural log of the Cis Isomer Absorbance against TimeTable 3 Slope, Y intercept and Regression erroneous belief Generated by Linest Function -0.01104-2.409360.000363640.0141620.9956790.015212921.71126840.213292050.000926CalculationsMass of Cis Isomer Required to Make 2 x 10-3 M 100mlM = Mass/(Volume Molar Mass)Mass req. = 2 10-3 ((100/1000) 285)= 57mgMass of Trans Isomer Required to Make 2 x 10-3 M 10mlM = Mass/(Volume Molar Mass)Mass req. = 2 10-3 ((10/1000) 285)= 5.7mgkk = (lnD0-D -lnDt-D) / tk =0.0092m-1lnDt-DlnD0-D-3.0718-2.5198Half lifet 1/2 =ln2/k=75.3422 minError PropagationMeasured weight of isomersCis 56.7mg Trans 5.7mgResolution of Scales Satorius Extend 0.1mgvolumetrical glassware100ml 0.1 ml A socio-economic class10ml 0.025 ml A ClassDiscussionMethanol was used as a solvent in this experiment to avoid the chemical interactions that may have occurred had water been used in its place (Mahaffy 2011). In the initial solution of the Cis isomer a ccuracy wasnt as important as it was being measured to find the optimum wavelength for analysis as seen in Figure 1 and Appendix 1. cooking of the Cis Isomer solution measured to produce Figure 2 required a mass of the compound as close as possible to the calculated amounts (See Results Calculations) in order to produce results that allowed for the accurate determination of the rate constant (k) and half-life (t1/2). The relationship between k and t1/2 is that k is a factor in the formula of t1/2 (See Results Calculations) and determines what unit of time that the half-life is expressed in (in this case minutes-1). Figure 1 plots the absorbance of the two isomers against the variant wavelengths from 350nm 700nm. From this interpret the wavelength of 540nm was identified as the ideal to be used to determine the reaction rate of the isomers. This was due to the topical anaesthetic maxima of the Cis isomer at this point which coincides with the local minima of the Trans isome r. This data is confirmed by the printout of the Varian Car 50 UV-Vis spectrometer which besides marked the 540nm point on its plot (see Appendix 1).This clear difference in absorption of the two isomers at this wavelength meant that the rate of inter-conversion could be determined. The graph of the natural logarithm of the absorbance of the Cis isomer against time can be seen in trope 2. By observing the points on the plot a straight draw off of decay confirms that this reaction is first order, a logarithm of the measured absorbance value (Christian 2010). Calculations were carried out on the data in table 2 to determine the k and t1/2 (see Results Calculations). The k value calculated of 0.0092 m-1 roughly matches the calculate generated by the linest function 0.01104m-1 (see Table 3, top left) and is also similar to the literature value of 0.00845m-1. With the calculated k value of 0.0092 the t1/2 was determined to be 75.3422 minutes. Slight variations between the k value ca lculated from the points in figure 2 and that generated by the linest function can be accounted for by the fact that the linest function is a calculated line of best fit and so does not fit the data points collected exactly but is an approximation. The discount difference between the literature value of k 0.00845m-1 and the calculated k of 0.0092m-1 can be accounted for by human error in time, volume and mass measurement. The range of error in this measurement is 0.00075 which is the difference between the calculated and literature values.ConclusionIn this experiment the rate constant (k) was determined to be 0.0092m-1 0.00075 and the t1/2 was calculated to be 75.3422 minutes.ReferencesBrasted, R. Hirayama C. 1958 The cis-trans Isomeration of Dichlorbis-(ethylenediamine)-cobalt(III) Chloride and Dichlorbis-(propylenediamine)-cobalt(III) Chloride in Alcohols, journal of chemical science, Department of Chemistry, University of Minnesota. Vol. 80 pp 788 794. Brown, T. LeMay H. Burst en, B. Murphy, C. Langford, S. & Sagatys D. 2010. Chemistry The Central Science, Pearson, Australia. pp 1196 1197. Christian, G. 2010. Analytical Chemistry 6th Ed., John Wiley & Sons, USA. pp 159, 270 271. Mahaffy, P. Bucat, B . Tasker, R. Kotz, J. Treichel, P. Weaver, G. & McMurry, J. 2011. Chemistry benignant Activity, Chemical Reactivity, Nelson Education, Canada. pp 99, 115 116.AppendicesAppendix 1 Figure 3 Absorbance of Cis and Trans Isomers at Various Wavelengths (Varian Car 50 UV-Vis spectrometer)