Phenylmagnesium bromide reaction with carbon dioxide

Reaction of a Grignard reagent with carbon dioxide, followed by treatment with aqueous HCI, gives a carboxylic acid. Propose a structural formula for the bracketed intermediate formed by the reaction of phenylmagnesium bromide with CO2, and propose a mechanism for the formation of this intermediate ... 

Reaction of Phenylmagnesium Bromide with Carbon Dioxide... 

Reaction Slowly pour the phenylmagnesium bromide solution onto the dry ice with vigorous swirling the mixture normally becomes rather viscous. Rinse the original round-bottom reaction flask with 2-3 ml of anhydrous diethyl ether and add this wash to the Erlenmeyer flask. Continue swirling the contents of the flask for a few minutes. After the addition is complete, cover the flask with a small watchglass or piece of filter paper and allow the excess carbon dioxide to sublime by letting the flask stand in the hood, properly labeled with your name, until the next laboratory period. ... 

Develop a protocol for investigating how using the normal mode addition of phenylmagnesium bromide and carbon dioxide affects the outcome of the reaction. You will need access to gaseous carbon dioxide to perform the reaction. Consult with your instructor before undertaking any experiments. 

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