Diethyl ether (CH₃CH₂–O–CH₂CH₃) and ethanol (CH₃CH₂–OH) both contain one oxygen atom. Which statement best explains why ethanol is much more water-soluble and has a higher boiling point?
AEthanol is larger and has more London dispersion forces
BEthanol has an O–H bond that allows hydrogen bonding with water; diethyl ether cannot donate hydrogen bonds
CDiethyl ether has a lower molecular weight so it evaporates faster
DEthanol contains a carbonyl group that interacts with water
The O–H bond in ethanol acts as a hydrogen-bond donor, allowing strong interactions with water molecules. Diethyl ether's oxygen can accept hydrogen bonds but cannot donate them (no O–H), so it is far less able to integrate into water's hydrogen-bond network. This single structural difference — the presence or absence of the O–H — is why the two compounds have such different physical properties despite the same molecular formula (C₂H₅OH vs. C₂H₅OC₂H₅).
Question 2 True / False
An ether (R–O–R') and an alcohol (R–OH) with the same molecular formula are constitutional isomers that generally have identical chemical reactivity because they contain the same atoms.
TTrue
FFalse
Answer: False
Same molecular formula does not mean same reactivity. Ethers lack the O–H bond and are comparatively inert — they resist oxidation and do not react with most nucleophiles. Alcohols, with their O–H, can be oxidized to aldehydes/ketones/carboxylic acids and undergo elimination and substitution reactions. The O–H bond is the reactive handle; without it, the oxygen's lone pairs are far less accessible. Reactivity is determined by functional group, not elemental composition.
Question 3 Short Answer
Why can a single drug molecule (like aspirin, which contains both an ester and a carboxylic acid) undergo two different types of reactions under different conditions?
Think about your answer, then reveal below.
Model answer: Each functional group reacts independently. The ester linkage can be hydrolyzed under acidic or basic aqueous conditions, while the carboxylic acid can react with bases, alcohols (to form new esters), or undergo decarboxylation. The hydrocarbon backbone is largely inert and does not interfere, so each functional group behaves according to its own chemistry.
This is the core principle of functional group analysis: the backbone sets the carbon skeleton but the chemistry happens at the functional groups, which can each be targeted selectively with the right reagent. Understanding this allows chemists to design multi-step syntheses that modify one group while leaving others intact.