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Why is benzene formed during Grignard reactions using phenylmagnesium bromide?
Wiki User
∙ 16y ago
Grignard reactions must be carried out in an anhydrous environment in an anhydrous solvent (e.g. anhydrous ether). Why? Grignard reagents behave essentially as a carbanion, and are extremely reactive. Therefore they cannot be carried out while acidic hydrogens, or other positive reactive centers are present (carbonyl compounds such as acetone) in the reaction mixture because there is no way to stop the Grignard from reacting with these other compounds rather than the desired reactant. If phenylmagnesium bromide were prepared, and ANY water was present in the reaction mixture phenylmagnesium bromide would not hesitate to react with water--stealing one of its hydrogens. This hydrogen would therefore replace the attached --MgBr to form benzene.
Wiki User
∙ 16y ago
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What is the melting point of phenylmagnesium bromide?
Phenylmagnesium bromide does not have a melting point. It is soluble in diethyl ether and THF and has a flash point of -45 degrees C.
What is gold III bromide?
Gold (III) bromide has the chemical formula AuBr3. It usually exists as a dimer with the formula Au2Br6. Gold (III) bromide may be used as a catalyst for Diels-Alder reactions.
How do you synthesize 2-phenylpropanal from benzene?
I can't say for sure, this isn't one I've thought much about but lets look at it logically. To a stable molecule like a benzene or an aryl group, there isn't much you can do in the absene of a catalyst. YOu can halogenate, formylate, acylate plus numerous more complex stuff. I think there would be a route via styrene oxide, at least there is in the literature. so for that youd acylate to acetophenone then reduce with borohydride then dehydrate to the alkene followed by performic acid epoxidation to styrene oxide. a grignard methyl magnesium bromide reagent will open the oxide to an alcohol in some percentage the direction you want and maybe a bit the opposite. Now you need to oxidize a terminal alcohol without over doing it and making the carboxylic acid and manganese dioxide is out because you need an adjacent double bond or benzene ring alfa to it to work Permanganate would be like taking a tank to a knife fight, dchromate would be ok in conjunction with pyridine, just get a text on oxidations or look at one online and you[ll find your answer. nitric acid is my go to choice for a terminal alchohol but it may be too much here, maybe very cold and slow addition of acid but it will be too much. good luck, that is a pretty significant sythesis problem for a student that is doing anything but advanced organic chemistry. alternatives would be a bromination of benzene to bromobenzene followed by a grignard with bromoethene to get styrene. start with benzaldehyde , do grignard with methylmagnesium bromide and dehydrate the alcohol start with benzonitrile and grignard with methylbromide to acetophenone reductions with borohydride can maybe use zinc instead or aluminum amalgam, certainly ataolysis with palladium solvents used would be thf or ether for grignards, the acylation of benzene could likely self solvate, the reduction with borohydride in methanol or methanol/dcm or water will work too. the best system here would be probably methanol/dcm, look at intermediates in sn1, sn2 reactions and you'll figure out why. remember you need an intermediate to form often when you want a reaction to go, if the intermediate is not compatible with the solvent it won't form.
If ethyl benzoate is treated with phenylmagnesium bromide a one to one mixture of benzophenone and triphenylmethanol are obtained after work-up. Why?
The MgBr causes the carbon that it's attached to in the phenylmagnesium bromide to become negative and attack the carbonyl carbon of the ethyl benzoate. The carbonly obtains a new bond with a phenyl group and loses its double bond to oxygen. It instead becomes a single bond and oxygen becomes negative (theoretically, the MgBr will attach to the oxygen as an intermediate phase). This attack of the carbon attached to the MgBr will happen a second time creating a carbon attached to 3 phenyl groups (triphenyl) and upon reduction of this compound (using H2 and a catalyst or LiAlH4), -OCH2CH3 gets protonated and leaves as ethanol, and the carbon and oxygen get protonated to CH3OH. I hope this makes sense to you, lol.
How will you synthesise ethyl bromide into propionic acid?
Convert the ethyl bromide into Grignard's reagent, ethyl magnesium bromide then allow to react with dry ice (Solid carbon dioxide) then acidic hydrolysis produces the propionic acid. CH3-Br + Mg --- anhydrous ether---> CH3-CH2-Mg-Br CH3-CH2-Mg-Br + CO2 ----H+/H2O---> CH3-CH2-COOH
If ethyl benzoate used to prepare triphenylmethanol is wet what byproduct is formed?
THIS IS A DIRECT QUOTE FROM YAHOO ANSWERS:Benzene and magnesium hydroxide and magnesium bromide.I am betting you are doing a Grignard reactionEthyl benzoate + 2 phenylmagnesium bromide --> triphenylmethanol•MgBr saltif water is present, the grignard reacts with the water firstPhenylmagnesium bromide + H2O --> benzene + MgOHBr
What is the melting point of phenylmagnesium bromide?
Phenylmagnesium bromide does not have a melting point. It is soluble in diethyl ether and THF and has a flash point of -45 degrees C.
Write the formula of grignard reagent and state the polar character?
A Grignard reagent or Grignard compound is a chemical compound with the generic formula R−Mg−X, where X is a halogen and R is an organic group, normally an alkyl or aryl. Two typical examples are methylmagnesium chloride Cl−Mg−CH3 and phenylmagnesium bromide (C6H5)−Mg−Br. They are a subclass of the organomagnesium compounds.
How do you do 1 1?
Reaction of cyclohexanone with 1-propyl magnesium bromide (a Grignard reagent) followed by hydrolysis.
How will you convert ethyl bromide in to propane?
Ethyl bromide react with Grignard reagentCH3-CH2-Br + CH3-Mg_Br
Structure of the compound formed when phenylmagnesium bromide reacts with acetophenone?
The structure of the compound formed is called 1,1-Diphenylethanol. The addition of a weak acid, such as aqueous ammonium chloride is needed for the reaction.
How do you synthesize 1-propylcyclohexan-1-ol?
Reaction of cyclohexanone with 1-propyl magnesium bromide (a Grignard reagent) followed by hydrolysis.
What is the impurity formed during the preparation of the Grignard reagent if phenyl bromide was used instead of bromobenzene?
Uses of phenyl in domestic purpose
What is the IUPAC name for a benzene ring with a branch of ketone?
benzen ch2br
What is the structure of p bromophenol?
Now this is a benzene ring with a Hydroxide on top, and a bromide on bottom; the p means opposite side
What is the structure of p-bromophenol?
Now this is a benzene ring with a Hydroxide on top, and a bromide on bottom; the p means opposite side
What has the author Gustaf Adolf Holmberg written?
Gustaf Adolf Holmberg has written: 'Hydrolysis of carbon-to-carbon bonds' -- subject(s): Hydrolysis, Molecules, Valence (Theoretical chemistry) 'The reactions between arylmagnesium bromides and ethyl 3-phenylchromone-2-carboxylate' -- subject(s): Carboxylates, Grignard reagents, Magnesium bromide, Reduction (Chemistry)
