What is the order of decreasing acidity for the molecules phenol, ethanoic acid and ethanol? Why?

Ethanoic acid is the most acidic of the three. This is because once ethanoic acid has lost a proton the negative charge can be spread over two oxygen atoms via two resonance forms. Oxygen atoms are electronegative, therefore happy to stabilise the negative charge resulting in a relatively stable ion. The next most acidic is phenol. Although more resonance forms can be drawn (4 in total) the majority of them (3) have the negative charge on the more electropositive atom carbon. This ion is therefore less stable than the ion formed from ethanoic acid as oxygen stabilises a negative charge better than carbon. Phenol is therefore less able to form the ion, therefore less acidic. The least acidic of the three is ethanol. This is because no resonance forms can be drawn for the resulting ion. This inability to delocalise the charge over the ion makes this the least stable ion. If the ion is the most unstable, ethanol must have the most difficulty to remove it's most acidic proton, making it the least acidic molecule of the three.

Related Chemistry A Level answers

All answers ▸

What is the difference between ionic and metallic bonding?


How do mass spectrometers work?


The ratio between the molar mass of an alkene(A) and an alkyne(B) with the same number of carbon atoms is 1.05. Find the molecular formulas of the two hydrocarbons then write the reaction for how we can obtain the alkene A from the alkyne B.


What is a transition metal?


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2024

Terms & Conditions|Privacy Policy