Experiment 10
Grignard Reactions
Name: Lidia Santiana Palha
Student number: s3333523
Email-address: lidiapalha@gmail.com
Name of demonstrator: H.Helbert
Reaction Equation
Summary
In this experiment a Grignard reaction was carried out to give the desired reagents: benzyl magnesium chloride. This was achieved by reacting benzyl chloride with magnesium in ether. After the Grignard’s reagents were formed, it was reacted with benzaldehyde in ether to give 1,2-diphenylethanol. The main objective of this experiment was to synthesize 1,2-diphenylethanol via a Grignard reaction. The NMR proves that the right product was formed in this experiment.
Introduction
The Grignard reaction is also known as an organometallic chemical reaction.
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The reaction is important for the formation of carbon –carbon bonds. Theory Fig.1 the reaction mechanism Grignard reaction is the formation of Grignard reagents this by the reaction between Mg and in this case an alkenyl halide.
Now looking in Fig.1 it shows how nucleophilic the Grignard’s reagents are. The carbon because partially negatively charged and the Chlorine to be partially positively charged. Due to this the Second part: first step shows how the nucleophile attacks the partially positively charged carbonyl and the electrons move to the oxygen atom making it negatively charged. The second step is protonation and this proton comes from the acid. The negative oxygen attacks the proton to give an alcohol.
Experimental
Making benzylmagnesium chloride.
All glassware is dried under N2 to remove all the oxygen. In a 250-ml three necked flask equipped with a reflux condenser (and a N2 line) and a dropping funnel, magnesium turnings (2.7g) were placed. A small crystal iodine was heated with a heat gun and produced purple vapour (this was done to activate the Mg). 5ml of dry diethyl ether was added slowly. Then a solution of benzyl chloride (6.5g) and diethyl ether (25ml). After the completion of the reaction, it was heated under reflux for 30 mins.
Synthesis of
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1,2-diphenylethanol. After the Grignard reagent formed, the dropping funnel was filled with a solution of benzaldehyde (47mmol) in diethyl ether (25ml).
It was added carefully. Then heated under reflux for 1 hour. After cooling to room temperature, the reaction was quenched by pouring the mixture into a beaker of ice and saturated ammonium chloride solution(20ml). The layers were separated and the aqueous layer was extracted with diethyl ether (2 x 20ml). The combined organic layers were washed with water and saturated aqueous NaCl solution, dried on NasSO4. After filtration, the mixture was put on the rotavap and the product crystallized. An NMR was taken to determine if the right product was
obtained. Results and discussion Fig.2 Analysis of Fig.2: D at 10.04ppm is a singlet that corresponds to the proton 15. A from 7.04 to7.7ppm is a multiplet that corresponds to the proton on carbon 1,2,3,4,5,6,9,10,11,12,13 and 14. B at 4.90 ppm is a triplet corresponds to the proton on carbon 7. C at 2.98ppm is a doublet that corresponds to the proton on carbon 8. The solvent chloroform used is showed at 7.26ppm. Conclusion The NMR proves that the Grignard reaction glassware was dried properly and that water didn’t ruin the reaction (water would protonate the reagent) because the product was formed. Bibliography https://en.wikipedia.org/wiki/Grignard_reaction
Then the reaction tube was capped but not tightly. The tube then was placed in a sand bath reflux to heat it until a brown color was formed. Then the tube was taken out of the sand bath and allowed to cool to room temperature. Then the tube was shaken until a formation of a white solid at the bottom of the tube. After formation of the white solid, diphenyl ether (2 mL) was added to the solution and heated until the white solid was completely dissolved in the solution. After heating, the tube was cooled to room temperature. Then toluene (2 mL) was added to the solution. The tube was then placed in an ice bath. Then the solution was filtered via vacuum filtration, and there was a formation of a white solid. Then the product was dried and weighed. The Final product was hexaphenylbenzene (0.094 g, 0.176 mmol,
Discussion and Conclusions: Interpreting these results have concluded that relative reactivity of these three anilines in order of most reactive to least reactive go; Aniline > Anisole > Acetanilide. Aniline, has an NH2 , the most active substituent , and adds to any ortho/para position available on the ring. This data is confirmed with the product obtained, (2,4,6 tribromoaniline, mp of 108-110 C). As for anisole, it has a strongly activating group attached, OMe an alkoxy group, and it added in two of the three available spots, both ortho. The results conclude: (2,4-Dibromoanisol mp 55-58 C ). Acetanilide has a strong activating group attached, acylamino group, but this group is large and the ortho positions are somewhat hindered so the majority of the product obtained added at the para position, results conclude: (p-bromoacetanilide mp 160-165 C). Since all the substituents attached to the aromatic rings were activators the only products able to be obtained were ortho/para products.
Solid triphenylmethanol (0.200 g, 0.768 mmol) and sulfuric acid (2 mL) were added to a reaction tube, which was then ground using a glass rod until it dissolved and turned a dark orange color. The mixture was then added dropwise via a glass pipette into another reaction tube containing methanol (1 mL). An extra amount of methanol (2 mL) was used to transfer the rest of the contents of the first reaction tube. Formation of crystals was facilitated by scratching the side of the tube and adding additional methanol until the color changed to an off-white color. The contents of the tube were then vacuum filtered with water and the resulting crude product was weighed and then recrystallized using hot methanol to form triphenylmethyl methyl ether (0.051 g, 0.186 mmol, 24.2%). The melting point was 81 – 83˚
In a separate beaker, acetone (0.587 mL, 8 mmol) and benzaldehyde (1.63 mL, 16 mmol) were charged with a stir bar and stirred on a magnetic stirrer. The beaker mixture was slowly added to the Erlenmeyer flask and stirred at room temperature for 30 minutes. Every 10 minutes, a small amount of the reaction mixture was spotted on a TLC plate, with an eluent mixture of ethyl acetate (2 mL) and hexanes (8 mL), to monitor the decrease in benzaldehyde via a UV light. When the reaction was complete, it was chilled in an ice bath until the product precipitated, which was then vacuum filtrated. The filter cake was washed with ice-cold 95% ethanol (2 x 10 mL) and 4% acetic acid in 95% ethanol (10 mL). The solid was fluffed and vacuum filtrated for about 15 minutes. The 0.688 g (2.9 mmol, 36.8%, 111.3-112.8 °C) product was analyzed via FTIR and 1H NMR spectroscopies, and the melting point was obtained via
Benzyl bromide, an unknown nucleophile and sodium hydroxide was synthesized to form a benzyl ether product. This product was purified and analyzed to find the unknown in the compound.
This process is then repeated. In the second trial, the Mg ribbon did not completely dissolve and the results were thrown out. The third trial (referred to as the second in the following analysis due to the exclusion of the previous one) was successful, and measurements can be seen below. We then moved onto the second reaction using magnesium oxide and hydrochloric acid in the fume hood. We measured 200.1 mL of HCl and placed it in the calorimeter, and an initial temperature reading was taken.
Cu (aq) + 2NO3 (aq) + 2Na+ (aq) + 2OH- (aq) → Cu(OH)2 (s) + 2Na+ (aq) + 2NO3(aq)
Aim: The aim of this experiment was to determine the empirical formula of magnesium oxide.
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The percentage yield gained was 70% from the Fischer Esterification reaction, which evaluates to be a good production of yield produced as the reaction is known to be reversible where conditions such as the concentration of the reactants, pressure and temperature could affect the extent of the reaction from performing. These white crystalline crystals were tested for impurity by conducting a melting point analysis and taking spectrospic data such as the IR spectra, HNMR and CNMR to confirm the identification of the product. These spectrospic methods and melting point analysis confirmed the white crystalline crystals were benzocaine.
The chemical reaction takes place when the magnesium ribbon is dropped. into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula equation for this experiment is: Mg + 2HCl (r) MgCl2 + H2. Magnesium + Hydrochloric acid (r) Magnesium Chloride + Hydrogen.
Chemical kinetics is a branch of chemistry that involves reaction rates and the steps that follow in. It tells you how fast a reaction can happen and the steps it takes to make complete the reaction (2). An application of chemical kinetics in everyday life is the mechanics of popcorn. The rate it pops depends on how much water is in a kernel. The more water it has the quicker the steam heats up and causes a reaction- the popping of the kernel (3). Catalysts, temperature, and concentration can cause variations in kinetics (4).
...ion, Proceedings of the 5th Annual International Conference on Remediation of Chlorinated and Recalcitrant Compounds, (2006) Monterey, CA, May 22-25.
Anthropologists study the behavior of various cultures and societies and try to understand why they believe and practice certain rituals. In the article Body Ritual Among The Nacirema, by Horace Miner and published by The American Anthropologist, the author describes extreme examples of ritual activity that focus on the human body. The Nacirema believe that the body is ugly, diseased, debilitated and in need of help from their local medicine men, "holy-mouth-men", and "listener" witchdoctor. Even though some of the practices are barbaric, I can relate some of the rituals to our own modern society. Economics is a large part of the ritual process.
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