Experiment preparation of cis and trans isomer PDF

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LABORATORY REPORTSKO 3013Basic OrganicChemistryDepartment of Chemistry Faculty of Science & MathematicsUniversiti Pendidikan Sultan IdrisExperiment : Preparation of Cis And TransIsomerGroup : BLECTURER : Dr Yuhanis Bt Mhd BakriNo. NameID Number1 Meerasri A/P Mariappan D2 Nur Najihah Binti Ab...

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LABORATORY REPORT

SKO 3013 Basic Organic Chemistry Department of Chemistry Faculty of Science & Mathematics Universiti Pendidikan Sultan Idris

Experiment : Preparation of Cis And Trans Isomer Group : B LECTURER : Dr Yuhanis Bt Mhd Bakri

No.

Nam e

ID Number

1

Meerasri A/P Mariappan

D2018108337

2

Nur Najihah Binti Abdullah Raman

D20181083311

Experiment 2 Title : PREPARATION OF CIS AND TRANS ISOMER 1. Objectives 1.1. 1.2. 2.

Synthesize fumaric acid from maleic acid Differentiate chemical and physical properties of each isomers

Introduction Malic acid and fumaric acid have the same molecular formula: C 4 H 4 O 4 . Each compound contains two carboxyl groups, -COOH, and a double bond. The compounds are isomers because their structures differ in the geometry, or arrangement in space of the atoms in the molecule. Cis-transisomers are a kind of stereoisomers called geometrical isomers. Due to the inability of rotation about the C=C bond, some compounds possess cis and trans isomers. Cis and trans isomers have different physical properties such as boiling point, solubility, density and stability.

4. Result

5. Discussion Part A In this experiment, maleic acid was converted to fumaric acid by heating it in concentrated HCl solution, a catalyst. The conversion of maleic acid to fumaric acid is guided by the general mechanism:

The melting point of the product, which is the fumaric acid, exhibits a melting point higher than the maleic acid.In this experiment, the melting point of fumaric acid is 270.3 ℃ while for the maleic acid 161 ℃ . Generally, the trans isomer has the higher melting point than the cis isomer. It is because trans isomers pack better than cis isomers. The "U" shape of the cis isomer doesn't pack as well as the straighter shape of the trans isomer. The poorer packing in the cis isomers means that the intermolecular forces aren't as effective as they should be and so less energy is needed tomelt the molecule which results a lower melting point. Also, trans isomers have higher meltingpoint because they are more stable than cis isomers. This stability arises due to their shape, transare straight which allows H intermolecular forces to increase and make the trans stable. It depending on the R groups, if they are next to each other ,it will increase the repulsion force between the substance, thus decreasing the melting point of cis. Also, as we can see, a concentrated HCl was used in the experiment rather than any inorganic catalysts such as iodine, bromine, hydrobromic acid, sulfuric acid, potassium thiocyanate and sodium bromide. Hydrochloric acid is a very efficient inversion catalyst and is soluble in the crude aqueous solution of maleic acid. Such a process for the preparation of fumaric acid involves heating an aqueous solution of maleic acid containing hydrochloric acid or other inversion catalysts such as an inorganic catalyst given above. As the inversion process progresses and fumaric acid is formed, the fumaric acid crystallizes out of the reaction mixture because o fits low solubility in the reaction mixture and the fumaric acid crystals are subsequently recovered by filtration or by centrifuging.

Part B Cis in acyclic systems, the cis isomers are more unstable than trans isomers. They have higher solubility in inert solvents.Trans in acyclic systems, the trans isomers are more stable than cis isomers. They have lower solubility in inert solvents.This is typically due to the increased unfavorable steric interaction of the substituents in the cis isomer. Therefore, trans isomers have a less-exothermic heat of combustion, indicating higher thermochemical stability. As can see maleic acid has higher solubility than fumaric acid. The molecules of maleic acidhave a stronger net dipole moment than fumaric acid. The molecules of maleic acid are polar and are easily hydrated by the polar water molecules. Moreover, the molecules of fumaric acid are more tightly packed compared with those of maleic acid. Question 1) Assume that equilibrium concentrations were achieved in Part A. Which acid is the most stable? Fumaric acid will be more stable. Refferences 1) Difference between Cis and trans | Difference between. (2018, May 31). https://www.differencebetween.net/science/difference-between-cis-and-trans/...