Synthesis and Separation Questions: 1. In what order do you expect ferrocene and

Question

Synthesis and Separation

Questions:

1. In what order do you expect ferrocene and two acetylferrocenes to come off the column? How the order of eluting aid in the sepatation process.

2. Why do ferrocene (max absorption-570nm), monoacetylferrocene (max absorption-590nm), and 1,1’ diacetylferrocene (max absorption-620nm) display colors at increasingly longer wavelengths?

3. Should you expect to be more moles of mono- or diacetylated ferrocene in the product mixture? Explain based on the reactivity of aromatic systems and substituted analogs.

Explanation / Answer

1) Ferrocene contains no functional group unlike acetylferrocene.

So ferrocene is non polar as compared to acetyl ferrocene, and hence due to less polarity the interaction between the stationary phase and ferrocen will be weak as compared to acetyl ferrocene. Hence the eluting order will be

Ferrocene then acetyferrocene

2) Due to presence of acetyl group the lamda max increases as the acetyl group acts as an auxochrome and it contributes in increasing conjugation of the compound and hence it can absrob a higher wavelength light.

So in diacetyl the absroption will be further be at more higher wavelength.

3) more of monoacetylated product as on introduction of acetyl group on aromatic ring its reactivity decreases as acetyl group is deactivating group and hence decreases the electron density on the aromatic ring making it less reactive for further attack by other electrophile

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