Question

The Zeisel method is an analytical procedure for determining the number of methoxyl groups in a compound. A weighed amount of the compound is heated with with concentrated HI, ether cleavage occurs, and the iodomethane product is distilled off and passed into an alcohol solution of AgNO3, where it reacts to form a precipitate of silver iodide. The AgI is then collected and weighed, and the percentage of methoxyl groups in the sample is thereby determined.

1.06 g of vanillin yields 1.64 g of AgI. If vanillin has a molecular weight of 152, how many methoxyl groups does vanillin contain?

Answer 1

1 molecule of vanilin contains 1 methoxy group

Step-by-step explanation:

In the Zeisel method 1 mole of AgI is equivalent to 1 mole of methoxyl group.

1,64g of AgI are:

1,64g AgI×
`(1mol)/(234,77gAgI)` = 6,99x10⁻³ moles of AgI ≡ moles of methoxy groups.

1,06g of vanilin are:

1,06g vanilin×
`(1mol)/(152gAgI)` = 6,97x10⁻³ moles of vanilin

The ratio of moles of methoxy groups/moles of vanilin is:

6,99x10⁻³ moles/6,97x10⁻³ moles = 1,00

That means that 1 molecule of vanilin contains 1 methoxy group.

I hope it helps