Synthesis and Characterization of the Polyhalogen Complex CsICl2 - Lab Report Example

Synthesis and Characterization of the Polyhalogen Complex CsICl2 Partner’s TA’s Section Number Introduction Theoretically, polyhalogens complexes are compounds containing one or multiple halogen ions attached to a single central atom. As a means of facilitating comprehension of polyhalogens complexes, practical experiments involving synthesis and characterization of these compounds are performed. This lab report covers on the laboratory preparation of Cs [ICl2]; a polyhalogen complex containing cesium as the central atom, and iodine and two chlorine ions as the attached halogens.

The main purpose of this experiment involved evaluation of a polyhalogen synthesis method coupled with structural characterization of the resultant complex using infrared spectroscopy technique. Theoretically, compounds absorb electromagnetic radiations at distinct frequencies depending on the inter-atomic bonds involved (Gibes 269). With the use of infrared radiations, a spectrum indicating the frequencies of absorptions can be produced. Subsequently, analyses of the spectral peaks enable determination and verification of a compound’s structure.

Subsequent sections of this report contain procedural steps used in synthesis and IR determination of Cs [ICl2] complex. Experimental ProceduresPrior to commencement of the lab exercise, appropriate safety measures were taken into consideration. These measures included the use of gloves in handling poisonous elements, specifically iodine. In addition, any stains of iodine on laboratory benches and laboratory equipment were cleaned to avoid contact of the poisonous element with skin and mucous membranes (Gibes 271).

Subsequently, the following Cs [ICl2] synthesis procedures were performed;i. A hot water bath at 90-95oC was prepared using a 600 ml beaker. ii. 2.002 g of Cs chloride and 1.508 g of iodine were quantitatively obtained.iii. The obtained Cs chloride was dissolved in water inside a test tube, followed by addition of iodine into the test tube.iv. The Cs chloride-iodine mixture was placed and maintained inside the 90-95oC water bathv. The heated mixture was placed inside a hood chamber, and chlorine gas dispensed through a gas dispersion tube into the mixture until all iodine dissolved.vi. The reacted mixture was cooled and filtered using Buchner funnel and suction filtration, and the resultant complex was purified by washing with cold water.

During synthesis, the following observations were made;The Cs chloride-iodine mixture turned from yellow to reddish upon heating in the 90-95oC water bath. Upon dispensation of chlorine into the mixture, color changed back from reddish to yellow and finally to white when the complex was washed and dried (Gibes 271). Data and ResultsQuantitative yield for the Cs [ICl2] complex was calculated and tabulated below. ItemMass (g)Watch glass55.538 Filter paper0.468Total mass of apparatus plus product56.

789Mass of product0.792Percentage yield = actual yield/theoretical yield x 100; 0.792/1.200 x 100 % yield = 66%Wavelength231 cm-1Besides quantitatively determining the mass of the produced Cs [ICl2], an infrared spectrum was obtained my subjecting the yielded compound through infrared spectroscopy. Discussions and ConclusionThe infrared spectrum of Cs ICl2 indicates presence of a single peak at a wavelength of 231 cm-1. Theoretically, this absorption wavelength is associated with the corresponding halogen; iodine.

In this context, a single point of absorption in a tri-atomic compound indicates the presence of a bending vibration with an asymmetrical structure (Smith 25). In this case, infrared spectrum of ICl2- provides a characteristic vibration peak similar to that exhibited by trigonal-planar molecular structures. ConclusionIn conclusion, the IR spectrum of Cs ICl2 verifies that the compound has a trigonal-planar molecular structure. The single peak in the infrared spectrum ascertains that the ICl2 anion in the complex have an asymmetrical center of vibration.

In this regard, it became evident that polyhalogens exhibit distinct molecular structures depending on the type of halogens present in a polyhalogen complex. In this case, the objective of infrared spectrum characterization was instrumental in determining the complex’s structure. Therefore, the synthesis and structure determination objectives of the experiment were sufficiently met. Post-Lab QuestionsQuestion 1: Predicting and Verifying Structure of ICl2-a. Lewis structure for [ICl2]- is [Cl – I – Cl]-b.

Oxidation number of iodine in Cs [ICl2] is given by Cs (1) + 2 Cl (-2) + I (x) = 0. Oxidation number of iodine (x) is -1.c. By predicting the structure of ICl2- using VSEPR theory, it emerged that the anion has a trigonal-planar structure. d. From the infrared spectrum stretching vibrations, peak absorption occurred at a single point, 231 cm-1. This single point of absorption associated with iodine indicates presence of a trigonal-planar geometric structure. Question 2: Comparing Infrared Spectrums of ICl2- versus XeF2Technically, ICl2- is a tri-halide ion while XeF2 is a di-halide compound.

In this case, XeF2 has a symmetrical center of vibration, thus its infrared spectrum would have two stretch frequency peaks at approximately 1365 cm-1. Contrarily, ICl2- lacks a symmetrical center of vibration. Therefore, the symmetrical stretching vibration of ICl2- is degenerate, hence the single-peaked infrared spectrum (Lindsey 106). Question 3: Thermal Decomposition of Cs [ICl2] versus KIUpon heating, Cs [ICl2] changes color from yellow to a whitish crystalline substance. The change in color can be attributed to the liberation of iodine as shown in the equation below.

Cs [ICl2] → CsCl + ICl, followed by 2 ICl → I2 + Cl2Since ICl is primarily unstable, it will dissociate further as 2 ICl → I2 + Cl2. Iodine is a volatile substance which sublimes from the heated compound leaving a whitish substance. Comparatively, heating KI as in the equation KI + O2 → K2O + I2 leaves a brownish substance because some brown iodine gas will remain embedded inside the resultant crystals of potassium oxide. Works CitedGibes, John. “Vibration Spectra and Structures of Tri-halide Ions.

” Journal of Molecular Structures 14.2 (2013): 267-273. Print.Lindsey, Helen. Structure Determination using Infrared Spectroscopy. Pittsburg: Cengage Learning, 2010. Print. Smith, George. Infrared and Raman Characteristic Group Frequencies: A Practical Approach. New York: John Wiley & Sons, 2009. Print.Appendix QuestionsQuestion 1: Stretching FrequenciesApparently, the stretching frequencies of halogens are all strong. Based on the Purdue database, it emerged that fluorine absorb at approximately 1365 cm-1, chlorine at 789 cm-1, bromine at 414 cm-1 and iodine at 265 cm-1.

In halogens, variance in stretching frequencies is associated with masses of molecules, and the respective transition energies of molecular bonds (Smith 39). Therefore, iodine has the highest transition frequency because it is not only massive than the other halogens, but also have the strongest bond transition energy. Similarly, variation in vibration frequencies of N2, O2 and F2 are associated with respective masses of the molecules. Question 2: Frequency SequenceFrom the website, the vibration frequency of HBr is out of sequence with the other hydrogen halides.

Question 3: Structures of AcetyleneBy using stretching frequencies, it is possible to distinguish the two molecular structures of acetylene. C-C stretching frequency for the first acetylene structure is 2100 – 2260 cm-1 while the C-C frequency in the second structure is 1620 – 1680 cm-1. On the other hand, these two structures will have distinct number of vibrations in the infrared spectrum. Based on the IR characteristics of the structurally analogous formaldehyde, it emerged that the first structure of acetylene will have 2 vibration numbers while the second structure will have 6 vibrations (Smith 19).