We can answer this by estimation if there is an obvious answer, or we could search the solubility data. Water is a polar compound, while ether is nonpolar. Ether is an organic solvent with a general formula of R-O-R, where R is a hydrocarbon chain.
1. The compound is butanol. Alcohols are polar, but as the hydrocarbon chain increases, the less it gets polar and become nonpolar. When the carbon chain is greater than 4 (butanol), the solubility in water decreases, while the solubility in ether increases. For butanol, it is slightly soluble in water than in ether.
2. CH₃C₆H₄NH₂ is an aromatic compound. Because this is nonpolar, it is soluble in ether.
3. CH₃C₆H₄NH₃⁺HSO₄⁻ is an ionized aromatic compound. So, this is also nonpolar. Moreover, sulfurous acid is also soluble in ether. Thus, this compound is more soluble in ether.
4. CH₃NH₂ is an amine. It contains a hydrogen bond (N-H), so it is polar. Thus, it is more soluble in water.
5. CH₃(CH₂)₄COOCH₃ is an ester. They are more polar than ethers, but less polar than alcohols. Because it has a pentane chain, it is more nonpolar than polar. Thus, this compound is more soluble in ether.
6. CH₃(CH₂)₈COOH is a carboxylic compound. These are polar if it contains at least 5 carbons. Since this contains 9 carbons, this is nonpolar. Thus, it is more soluble in ether.
7. CH₃(CH₂)₈COO⁻Na⁺ is a carboxylate ion. Because it has an ion, this is more soluble in water, such that it dissociates Na⁺ from CH₃(CH₂)₈COO⁻.
