LAB 7: ORGANOMETALLIC REACTIONS: IDENTIFICATION OF AN UNKNOWN BROMIDE (Preparative)
Introduction
The first purpose of the lab was to prepare an unknown organomagnesium bromide, an organometallic reagent, reacting an unknown aryl bromide with magnesium in anhydrous ether. The unknown was chosen from a predetermined list of benzoic acid derivatives with varying molecular weights and melting points (see Supplement C). The second purpose of this lab was to prepare an unknown carboxylic acid by reacting the unknown aryl-magnesium bromide with carbon dioxide and diethyl ether then protonating.The third purpose of this lab was to determine the neutralization equivalence point of the unknown carboxylic acid by titrating with sodium hydroxide. The fourth purpose of this lab was to ascertain the identity of the unknown carboxylic acid, and thus the original unknown aryl bromide, using its molecular weight determined from neutralization and melting point.
Data and Results
Compound
Molecular Weight (g/mol)
Melting Point (°C)
Unknown Carboxylic Acid (R--COOH)
121.18
116-119
Discussion
Organometallic reagents are compounds with carbon-metal (R--M) bond. In the carbon-metal bond, carbon is more electronegative than the metal atom which creates a dipole moment where carbon possesses a partial negative charge and the metal atom possessing a partial positive charge (Rδ---Mδ+). The partial negative charge on the carbon allows it to act as a strong nucleophile or base similar to
In the Cannizaro reaction an aldehyde is simultaneously reduced into its primary alcohol form and also oxidized into it 's carboxylic acid form. The purpose of this experiment is to isolate, purify and identify compounds 1 and 2 which contain 4-chlorobenzaldehyde, methanol, and aqueous potassium hydroxide. Compounds 1 and 2 are purified by crystallization. . The purified product will be characterized by IR spectroscopy and melting point.
In this experiment, the goal is to prepare a Grignard reagent from an unknown aryl halide and identify the identity of the aryl halide by converting it to a carboxylic acid to determine its melting point and molar mass (determined by titration). The experiment began by dissolving 0.25g of magnesium powder in a 25mL round-bottom with 5mL of anhydrous ether and stirring with a stir bar. Then the round-bottom flask was set up for reflux using a Claisen adapter where the vertical part is covered with a septum to prevent air from mixed with the solution. The septum is very important because the Grignard product can react with oxygen to produces a carboxylic acid, which is not wanted. Also, the choice of anhydrous solvent is important because the Grignard product can react with water to produce an alkane. With the reflux set up, the next step was to add the halide. 1.2mL of the unknown bromoarene mixed with 2.5mL ether was slowly added dropwise through the septum using the needle and syringe. The bromoarene had to be added slowly because there Grignard product would undergo another unwanted side reaction by reacting with the unknown bromoarene. The product with be a new carbon-carbon bond between the unknown bromoarene and the Grignard product. If the bromoarene is added slowly, the chances of the Grignard product reacting with the bromoarene over the magnesium is low because magnesium exists in larger concentration in the solution. Once all the unknown bromoarene
A Grignard reagent is a type of organometallic, which consists of a bond between a metal and a carbon. There are three types of carbon-metal bonds: ionic, polar covalent, and
6. Purpose: to clarify the mechanism for the cycloaddition reaction between benzonitrile oxide and an alkene, and to test the regiochemistry of the reaction between benzonitrile oxide and styrene; to purify the crude product of either trans-stilbene, cis-stilbene, or styrene reaction.
The purpose of this experiment is to examine the reactivities of various alkyl halides under both SN2 and SN1 reaction conditions. The alkyl halides will be examined based on the substrate types and solvent the reaction takes place in.
The Grignard reaction is an important synthetic process by which a new carbon to carbon bond is formed. Magnesium metal is first reacted with an organic halide forming the Grignard reagent. The Grignard reaction is the addition of an organomagnesium halide (Grignard reagent) to a ketone or aldehyde, to form a tertiary or secondary alcohol, respectively. For example, the reaction with formaldehyde leads to a primary alcohol. Grignard Reagents are also used in the following important reactions: The addition of an excess of a Grignard reagent to an ester or lactone gives a tertiary alcohol in which two alkyl groups are the same, and the addition of a
As the acid was being added, the mixture was being stirred over a stir plate. Once completed, the reaction mixture was poured from the round bottom flask into a 500 mL separatory funnel and its top (organic) layer was extracted into another beaker. The bottom (aqueous) layer was placed back into the funnel and extracted twice with 50.0 mL of ethyl ether each. The newly extracted layers were combined and dried over magnesium sulfate (MgSO4). The dried solution was the decanted into a beaker to remove the MgSO4 salts and the product solution was collected via Buchner vacuum filtration. The resulting product was transferred into an Erlenmeyer flask with an inverted beaker on top and stored in a drawer.
The original 1.0 gram of the 50/50 mixture of the benzoic acid and benzil contain 0.5 gram of benzil. Thus, from 0.5 gram of benzil, only 0.266 gram of benzil was collected. The percent recovery of benzil was calculated to be 53.2%. This low percent recovery could be due to filtration errors. Some amount of benzil remained on the filtration paper that contained the MgSO4. In order for determining the purity of the
6. Summarize in a few sentences the halogenation and controlled oxidation reactions of 1°, 2°, and 3° alcohols.
Theory: One of the methods of preparing alkyl halides is via the nucleophilic substitution reactions of alcohols. Alcohols are inexpensive materials and easy to maintain. However, they are a poor leaving group the OH group is a problem in nucleophilic substitution, this problem is fixed by converting the alcohol into H2O.
Grignard was the child of a sail producer. In the wake of concentrating on arithmetic at Lyon he exchanged to science and found the manufactured response bearing his name (the Grignard response) in 1900. He turned into an educator at the University of Nancy in 1910 and was granted the Nobel Prize in Chemistry in 1912. Amid World War I, he studied chemical warfare agents, especially the produce of phosgene and the identification of mustard gas. His partner on the German side was another Nobel Prize–winning chemist, Fritz Haber. (2) The Grignard reagent is exceptionally responsive and responds with most natural mixes. It likewise responds with water, carbon dioxide and oxygen. (2) Grignard reagents are set up by the response of magnesium metal with fitting alkyl halide in ether dissolvable. The halogen might be Cl, Br, or I. A standout amongst the most imperative employments of the Grignard Reagent is the response with aldehydes and ketones to frame liquor. A related blend utilizes ethylene oxide to plan alcohols containing two more carbon molecules than that of the alkyl halide. (2)
Objective: The objective of this experiment is to use acid-base extraction techniques to separate a mixture of organic compounds based on acidity and/or basicity. After the three compounds are separated we will recover them into their salt forms and then purify them by recrystallization and identify them by their melting points.
In this experiment, we were given three main goals to accomplish. We were to identify the compound through a series of organized experiments and analyze as many physical chemical properties as possible.
Organometallic are the most commonly compounds used in homogeneous catalysis. They usually contain various kinds of metals. Their reactivity, bonding (ionic and covalent or in-between) and stabilities are premised on 18 electrons rule. Organometallic compounds contain at least 1 carbon to metal bond. There are also organometallic complexes which have covalent bonds between organic ligands and a metal. The metal binds to ligands through an atom e.g. O2 or N; such compounds are referred to as coordination compounds. The complexes are basic in nature, also as reducing agents act as superoxide anion scavengers which help in catalyzing polymerization reactions and thus used clinically to treat tissues and cell injuries be it lymphomas or carcinomas. Rhodium compounds is analogues to the corresponding Platinum and Ruthenium compounds serve as effective anticancer agents due to significant antitumor properties. Effective advanced technologies such as nuclear magnetic resonance (NMR) and infrared spectroscopy (IR) are used to determine the dynamic properties, structures and industrial uses of organometallic compounds and complexes due to the ability to absorb the available proton occupied each site of a metal atom in the solution.
Coordination chemistry, which is the chemistry of metal complexes, is an important and fascinating branch of chemistry. The coordination compounds including organometallics are of significant importance and play a pivotal role in industry, technology and life processes. Due to their potential applications in various fields it has always fascinated and inspired chemists all over the world. This can be evidenced by the vast prolificity and scope of research papers on the subject in recent times and also by the diversity in which it has found applications.