A Grignard-Like Organic Reaction
The Synthesis of 1-phenyl-3-buten-1-ol
Introduction
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
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The reaction is carried out in saturated aqueous ammonium chloride solution. Thus no special drying of solvents, reagents, or glassware is required. The reaction mechanism for this experiment can be seen below (Fig. 2)
DATA | | | | | | Obtained Values | | | | | | Weight of Zinc powder | 0.165 g | | | | | Volume of NH4Cl (aq) | 1.0 mL | | | | | Volume of Benzaldehyde | 0.105 mL | | | | | Volume of THF | 0.5 mL | | | | | Volume of Allyl Bromide | 0.205 mL | | | | | Weight of Final Product | 0.0514 g | | | | | | | | | | | Percent Yield * | | | | | | Compound | Expected | Actual | % | | | 1-phenyl-3-buten-1-ol | 0.153 g | 0.0514 g | 33.60% | | | | | | | | | TLC | | | | | | solvent system: 30% ether-hexane | | | | | Compound | Rf Value | | | | | Benzaldehyde | 0.75 | | | | | 1-phenyl-3-buten-1-ol | 0.25 | | | | | | | | | | | * Please see calculation section Fig. 3 for further details. | | | | | | | | | | | | | | | Density (g/cm3) ++ | | | Formula Weight (g/mol) ++ | Compound | | | Zinc | 65.38 | | Benzaldehyde | 1.04 | | Benzaldehyde | 106.12 | | 1-phenyl-3-buten-1-ol | 0.992 | | Allyl Bromide | 120.99 | | NH4Cl (aq) | 1.53 | | 1-phenyl-3-buten-1-ol | 148.2 | | THF | 0.8892 | | Allyl Zinc Bromide | 186.37 | | Allyl Bromide | 1.40 | | | | | Diethyl Ether | 0.7134 | |
Any amount of H2O present would react with and therefore ruin the Grignard reagent. The negative charge on the Grignard carbon would pop a proton off of water, and the resulting hydroxide would react with MgBr2. Since all of the water and moisture was removed, the reaction should run successfully. For this experiment’s reaction, bromobenzene is turned into phenylmagnesium bromide, a Grignard reagent. Then, the Grignard reagent is reacted with benzophenone to yield a molecule with a negative charge on the oxygen. This molecule is worked up and protonated to yield triphenylmethanol.
Reaction 2 - 1.Used a Beral- type pipet, added about 2mL (40 Drops) of 1M hydrochloric acid solution to a small test tube.
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
The synthesis of the alkyl halide n-Butyl Bromide from alcohol is the foundation for the experiment. During the isolation of the n-butyl bromide, the crude product is washed with sulfuric acid, water, and sodium bicarbonate to remove any remaining acid or n-butyl alcohol. The primary alkyl halide halide n-butyl bromide is prepared by allowing n-butyl alcohol to react with sodium bromide and sulfuric acid. The sodium bromide reacts with sulfuric acid to produce hydrobromic acid . Excess sulfuric acid acts to shift the equilibrium and speed up the reaction by producing a higher concentration of hydrobromic acid. The
As detailed in Pavia 's Organic Laboratory techniques the reaction is expected to proceed via the following reaction:
Organometallic compounds, such as Grignard reagents, are molecules containing carbon-metal bonds and are often used to create new carbon-carbon bonds. Grignard reagents—or organomagnesims— are specifically those that have a carbon-magnesium bond.
Reaction 1 involved a primary alcohol (OH), weak leaving group in the starting material and a reaction with a strong nucleophile (sodium bromide) and a polar protic solvent (sulfuric acid). The reaction was carried out through reflux and the product had a relatively high yield (75%) (Scheme 1).
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Wash (swirl and shake) the organic layer with one 10-mL portion of water and again drain the lower aqueous layer. Transfer the organic layer to a small, dry Erlenmeyer flask by pouring it from the top of the separatory funnel. Dry the crude t-pentyl chloride over 1.01 g of anhydrous calcium chloride until it is clear (see Technique 12, Section 12.9). Swirl the alkyl halide with the drying agent to aid the drying.
The solution that was performed in this experiment was to use sulfuric acid in order to form a protonated alcohol, so when the halogen or nucleophile back attacks the compound, water is displaced. Once the alcohol is protonated, the solution reacts in either an SN1 or SN2 mechanism.
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The reaction took place in a conical vial and .2mL of each of the reactant samples were added to it along with some 95% ethanol. Two drops of NaOH were added shortly after and stirred at room temperature for fifteen minutes. The vial was cooled in and ice bath and crystallized. Vacuum filtration was performed to filter the crude product. The crude product was recrystallized using methanol and filtered again. We made one change to the procedure and instead of using .7mL of ethanol we
Through the use of the Grignard reaction, a carbon-carbon bond was formed, thereby resulting in the formation of triphenylmethanol from phenyl magnesium bromide and benzophenone. A recrystallization was performed to purify the Grignard product by dissolving the product in methanol. From here, a melting point range of 147.0 °C to 150.8 °C was obtained. The purified product yielded an IR spectrum with major peaks of 3471.82 cm-1, 3060.90 cm-1, 1597.38 cm-1, and 1489.64 cm-1, which helped to testify whether the identity of the product matched the expected triphenylmethanol. The identity of the product being correct was further confirmed by way of both proton and carbon-13 NMR spectra. This is due to the fact
The procedure was performed as follows: For run 1, 20cm3 of acetone, 10cm3 of sulphuric acid and 145cm3 of water was added to a conical flask. 25cm3 of iodine was then added to this solution which started the reaction and immediately, 20cm3