Discussion The purpose of this lab was to properly prepare a Grignard reagent from an unknown aryl halide and then to use the prepared Grignard reagent with solid carbon dioxide and an acid quench to form a carboxylic acid. Organometallics are compounds that have a carbon bonded to a metal; C-M, where M is any transition metal. In an organometallic, the carbon has a partial negative charge and is considered electron-rich due to the bond with the positively charged metal. Because of this partial negative charge, the carbon acts as a nucleophile and is able to be used in reactions to produce new bonds between carbon atoms by attaching to another carbon that acts as an electrophile. Grignard reagents specifically are organometallics that have …show more content…
In order to control this rate, the halide should be added slowly, dropwise and the reaction should be placed in an ice water bath following completion. Some side reactions that could occur when preparing a Grignard are the Grignard with water which destroys the Grignard reagent and forms a hydrocarbon and magnesium salt. This is why keeping and using equipment that was dry was so important as well as using an aprotic solvent and reacting in air that is not humid/full of moisture. Two side reactions that are problematic but are not usually a concern are the Grignard with either O2 or CO2. These are negligible side reactions because the O2/CO2 present in the diethyl ether solvent is very small. Another problematic side reaction that cannot be avoided but can be minimized is the coupling reaction of the Grignard with the halide which forms a symmetrical hydrocarbon. This coupling reaction is minimized by keeping the concentration of the halide low and using dilute solutions done by keeping the reaction stirring and adding in halide slowly. At the end of this reaction, there comes a point where the original halide is more likely to react with the Grignard reagent than it is with the …show more content…
This number was found by dividing the 0.282 g by the number of moles of NaOH, 0.00201 moles (which was found by dividing the 20.1 mL used by 1000 and multiplying that number by the 0.1 M concentration). The molecular weight data can be used to compare and identify experimental data to that of known data in order to identify the unknown. The known molecular weight of benzoic acid is 122.12 g/mol, so there were errors in obtaining the molecular weight from the lab as the lab molecular weight is almost 20 g/mol higher. These errors could have been caused by impurities remaining in the final product such as the previously used/present magnesium, iodine, or the original
After 28 minutes, the mixture stopped boiling, and approximately 4.5 ml of bromobenzene was added drop by drop in the mixture, and color of the mixture was turned light brown orange. Then, the phenylmagnesium bromide was cooled in ice bath for a few minutes, and 10 ml of anhydrous diethyl ether was added in the mixture by using the syringe. After that, approximately 2.3 ml of methyl benzoate was added to the reaction, and it was added slowly slowly because the reaction was exothermic which needed to be cool in order to maintain a gentle reflux. Once all the methyl benzoate solution was added, the heating mantle was removed from the reaction flask and was cooled to the room temperature. During the reaction, a milky white salt began to precipitate, and the reaction flask was swirled for ten minutes until most of the reaction became visibly subdivided.
Marissa De la Paz 29 October 2015 Landstrom T/R, 8am Experiment 13B: Phenyl Grignard Addition to Benzophenone The objective of this experiment is to first generate a Grignard reagent, then use that to synthesize triphenylmethanol. The Grignard reagent is necessary to create a new C—C bond. The formation of triphenylmethanol is broken down in several steps.
In this test, primary halides precipitate the fastest while secondary halides need to be heated in order for a reaction to occur. Comparison of the rates of precipitation of the obtained product to standard 1° and 2° bromide solutions will show whether the product is a primary or secondary
In the first step, the leaving group departs, forming a carbocation C+. In the second step, the nucleophilic reagent (Nuc :) attaches to the carbocation and forms a covalent sigma bond. If the substrate has a chiral carbon, this mechanism can result in either inversion of the stereochemistry or retention of configuration. Usually both occur without preference. The result is racemization.
Introduction SN2 stands for substitution, nucleophilic, bimolecular and occurs in one step where the nucleophile and electrophile react: the nucleophile attacks the electrophile 180° from the leaving group.3 The leaving group is nothing more than a group that leaves the electrophile attacked by the nucleophile. In this experiment the nucleophile is bromide, the electrophile is 1-butanol, and the leaving group is hydroxide. However, bromide must first be obtained from hydrobromic acid which gets bromide from a reaction between sodium bromide and sulfuric acid. The hydrogen and bromide in hydrobromic acid reacts with the oxygen in 1-butanol and the carbon attached to oxygen respectively to form 1-bromobutane. The overall reaction of this procedure
#24 was assigned. During the first week of the experiment, the Grignard reagent was prepared from an alkyl bromide and magnesium. During the hydrolysis,
In a two-day experiment, an SN2 reaction was conducted and benzyl bromide, sodium hydroxide, and an unknown were used. In a nucleophilic substitution reaction, the nucleophile and the alkyl carbon determine if the reaction is an SN2 or SN1 reaction. In an SN2 reaction, the process occurs in one step and works best with a primary carbon along with a strong nucleophile. During the experiment, recrystallization was used to purified the product; meanwhile, the melting point range and thin layer chromatography (TLC) data were used to identify the product of the reaction. After the completion, the unknown chemical was determined as 4-chlorobenzyl phenyl ether.
The reaction was allowed to proceed for 30 minutes and was subsequently quenched using hydrochloric acid. The addition of hydrochloric acid permitted the protonation of the reduced ketone (O-) to form the two diastereomer
Identifying reaction types and calculating percent yield after multiple chemical reactions of copper metal *Ashlyn Langner and Katherine Rumfield Chemistry 111 Section 524 Introduction A topic of interest in science is the evaluation of the law of conservation of matter through different types of chemical reactions and determining the percent yield resulting from these reactions. This law states that after a chemical reaction, matter should neither be created nor destroyed. This experiment allows for this law to be tested and for the determination of different errors that may occur during chemical reactions similar to this one. The magnitude of these errors can be found through the percent yield calculated by using the original mass of
Chem 51 LB Experiment 3 Report Scaffold: Bromination of Trans-Cinnamic Acid 1. The goal of this experiment was to perform a halogenation reaction through the addition of two bromides from pyridinium tribromide. This was accomplished by reacting trans-cinnamic acid with pyridinium tribromide. After the reaction took place, melting point analysis was conducted to find out the stereochemistry of the product, which could either be syn-addition, anti-addition, or syn + anti-addition. 2.
The purpose of this experiment is to perform a two step reductive amination using o-vanillin with p-toluidine to synthesize an imine derivative. In this experiment, 0.386 g of o-vanillin and 0.276 g of p-toluidine were mixed into an Erlenmeyer flask. The o-vanillin turned from a green powder to orange layer as it mixed with p-toludine, which was originally a white solid. Ethanol was added as a solvent for this reaction. Sodium borohydride was added in slow portion as the reducing agent, dissolving the precipitate into a yellowish lime solution.
The purpose of this experiment was to learn about metal hydride reduction reactions. Therefore, the sodium borohydride reduction of the ketone, 9-fluorenone was performed to yield the secondary alcohol, 9-fluorenol. Reduction of an organic molecule usually corresponds to decreasing its oxygen content or increasing its hydrogen content. In order to achieve such a chemical change, sodium borohydride (NaBH4) is used as a reducing agent. There are other metal hydrides used in the reduction of carbonyl groups such as lithium aluminum hydride (LiAlH4).
Hence, a calcium chloride and cotton were filled inside a drying tube. The condenser was wrapped with parafilm and a paper towel to avoid moistures from entering. The reagent will act as nucleophilic addition to acetone and work up with hydrochloride acid to synthesize 2-methylhexanol. Throughout this process, the solution turns dark grey and develop white precipitates.
The Wittig reaction is valuable reaction. It has unique properties that allows for a carbon=carbon double bond to form from where a C=O double bond used to be located. Creating additional C=C double bonds is valuable due to its use in synthesis. The Wittig reaction will allow the synthesis of Stilbene (E and Z) from a Benzaldehyde (Ketcha, 141).
If only one reactant is increased, then the chemical reaction will only produce a certain amount of products after the limiting reagent is used up, and in this experiment, the most mass the reaction could produce was 0.4 grams. Although we kept adding calcium chloride, not adding sodium hydroxide in the same proportions will not yield more product, which is the main goal in conducting this lab. We should have seen a plateau at 0.4 grams to show that the limiting reagent inhibited further Ca(OH)2 production, but we made several mistakes in our experiment, which made the data unusable to conclude. Once again, the data is polluted, so these number are not accurate, but it is the data our group has to work with. The theoretical yield should have been more than the actual yield, and the percentages should have been less than 100.