Final answer:
The structure of the compound with molecular formula C4H4O3 is likely maleic anhydride, which releases 3 moles of gas upon reaction with methyl magnesium bromide due to the formation of two alcohols and the release of one mole of carboxylic acid along with 3 moles of CO2.
Step-by-step explanation:
To identify the structure of the compound with molecular formula C4H4O3 that releases 3 moles of gas upon treatment with methyl magnesium bromide, we must consider the possible organic structures that fit this formula. The treatment with methyl magnesium bromide suggests a Grignard reaction, which typically involves the reaction of a carbonyl group. Given the molecular formula and the release of 3 moles of gas, the most likely structure is the anhydride formed between two carboxylic acid molecules since, upon reaction with a Grignard reagent, it could generate two moles of alcohol and one mole of carboxylic acid, releasing 3 moles of gas (CO2) in the process.
The structure most consistent with these observations and the molecular formula C4H4O3 is maleic anhydride:
CH2=C(C=O)O(C=O)CH2
Here, the carbon-carbon double bond remains intact while each of the cyclic anhydride carbons reacts with the Grignard reagent to produce the aforementioned gases and compounds.