The crystal packing exhibits a herringbone structure. By adhering to this procedure, it would likely reduce both the amount of impurities present within the supplied chemicals, and also aid in the recovery of the product. The major flaw in the process occurred when the product was extracted from the reaction tube, although the tube was rinsed twice with water it is almost impossible to transport the entirety of the crystal product. The deviations in results both of the actual percentage yield vs. An approximate isotropic treatment of cell e. Experimental In a 50-ml Erlenmeyer flask were placed 690 mg 5 mmol of 1,4-dimethoxybenzene, 1. It is likely that throughout the reaction process the chemical samples used will be introduced to various contaminates, either through the extraction of a chemical from its original container due to multiple lab groups extracting from the same source and also through exposure to the lab environment before its testing, which will allow the chemical to deviate from specific analytical data.
This is one of the drawback of this reaction. The two chlorine atoms of dichloromehtane methylene chloride are replaced by benzene rings. Through this process a product of 56. It is suggested that the curling may be due to differential adsorption of the solvent on opposite faces of the plates. The carbocation from 3-methyl-2-butanol undergoes a hydride shift, and hence, both reactions afford 1,4-bis 1,1-dimethylpropyl -2,5-dimethoxybenzene in high yields. This complex may act as the electrophilic reagent or it may dissociate to give a free carbocation, which can act as electrophile. To apply the reaction of Friedel-Crafts Alkylation to dimethoxybenzene Chemical Index: Chemical Structure Molecular Weight Melting Point Boiling Point Acetic Acid C2H4O2 60.
They attack the electron deficient carbocation to form the σ-complex. The product, 1,4-di- tert-butyl-2,5-dimethoxybenzene, I , has also been reported to exhibit a dramatic change of shape during crystal growth Blatchly and Hartshorne, 1966. © 1999 International Union of Crystallography Printed in Great Britain - all rights reserved. Stir the mixture thoroughly with a glass stirring rod, remove reaction tube from ice bath and allow the solution to reach room temperature approximately 15 minutes. Students will prepare the product the first week of the experiment.
The replacement of fourth halogen atom is not possible due to steric hindrance. When 1,4-dimethoxybenzene reacts with the carbocation generated from tert-butyl alcohol, a trisubstituted product, 1-tert-butyl-2,5-dimethoxybenzene is generated. The crystal structure of I has already been reported Rosokha and Kochi, 2007. The meta substitutions occur due to less steric interactions. Friedel-Crafts alkylation of benzene and substituted benzenes involves substituting a hydrogen atom on a benzene ring with an alkyl group. The Friedel-Crafts alkylation involves the electrophilic substitution of alkyl groups on aromatic rings when arenes are treated with alkyl halides in presence of Lewis acids. Macroscale and Microscale Organic Experiments.
Sulfuric acid can also be used as catalyst. Thus, it is impossible to determine whether or not the product is actually 1, 4-Di-t-butyl-2, 5 — dimethoxybenzene and that the reaction was successful. The proton is added to the the doubly bonded carbon so as to generate the more stable carbocation. Students determine the product identity from the spectroscopy results. This work was partially supported by a Grant-in-Aid for Young Scientists B grant No. A further study has been made of the curling during growth of thin crystal plates of 2,5-di-t-butyl-1,4-dimethoxybenzene, and this behaviour has been related to the approximate structure of the compound deduced from its optical properties.
This new module also includes the ability to perform packing similarity calculations between structures containing the same compound. Without further analysis it is impossible to determine whether or not the Friedel-Crafts alkylation reaction and the experiment were successful. The weighted R-factor wR and goodness of fit S are based on F 2, conventional R-factors R are based on F, with F set to zero for negative F 2. The complete molecule is generated by the application of a crystallographic centre of inversion. Comment Electrophilic aromatic substitution is one of the key reactions in organic chemistry. This reaction occurs by treatment of benzene or substituted benzene with a stable carbocation. If this experiment were to be repeated in order to compare the results to the previously conducted experiment, it would be suggested that the procedure explicitly adhere to the procedure outlined by the text book, Macroscale and Microscale Organic Experiments 6th Edition by Kenneth L.
Allow the reaction product to dry completely and then determine percent yield and melting point. Hence the major product is cumene rather than propyl benzene. Concentrated sulfuric acid 5 ml was added dropwise into the vigorously stirred reaction mixture so as not to exceed the temperature of 283 K. For instance, the melting point determined through this lab was 71. The methyl C—H of the methoxy group points to the adjacent benzene ring in a face-on-edge manner, in which the distance between the methyl carbon and the π-plane is 3. The bright yellow crystallized product was analyzed to achieve a melting point of 71.
Several reviews have been published. A new module of functionality has been produced, called the Materials Module, which allows highly customizable searching of structural databases for intermolecular interaction motifs and packing patterns. Melting point and gas chromatography confirm that the products are identical, promoting discussion of carbocation stability and the hydride shift mechanism. Students determine the product identity from the spectroscopy results. A Wagner—Meerwein rearrangement is a class of in which a , or group migrates from one carbon to a neighboring carbon. Alternatively, the carbocation may be generated from an alkyl halide upon treatment with an aluminum halide Figure 3.
Carbocations may be generated from alcohols or alkenes through treatment with strong acid. Although the product was allowed to dry for a couple days, it was never washed with a solvent such as methanol to reduce the impurities within the product. In this discovery laboratory, students performed electrophilic aromatic substitution reactions between 1,4-dimethoxybenzene and either 2-methyl-2-butanol or 3-methyl-2-butanol with sulfuric acid as a catalyst. . The title compound, C 18H 30O 2, was prepared by Friedel—Crafts alkylation of 1,4-dimethoxybenzene with 2-methyl-2-butanol. In this reaction, t-butyl carbocation is generated via dehydration of protonated alcohol. The pi electrons of one of the pi bonds C 1-C 2 of benzene is used to form a new bond between C 2 and the carbon atom of the carbocation.