Question

question 10 (1 point)
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which of the following would be the least soluble in water?
a) ch₃ch₂ch₂ch₂nh₂
b) ch₃ch₂nh₂
c) ch₃ch₂ch₂ch₂ch₂ch₂nh₂
d) ch₃nh₂
e) ch₃ch₂ch₂nh₂

Explanation:

Step1: Solubility principle

Solubility in water depends on the balance between the hydrophilic (water - loving) and hydrophobic (water - hating) parts of a molecule. Amines (\(-NH_2\)) are hydrophilic due to their ability to form hydrogen bonds with water. The hydrocarbon chain (\(CH_3(CH_2)_n-\)) is hydrophobic.

Step2: Analyze hydrocarbon chain length

As the length of the hydrocarbon chain (\(n\)) increases, the hydrophobic effect becomes more dominant.

• For \(CH_3NH_2\) (\(n = 0\)), the hydrophobic part is very small.
• For \(CH_3CH_2NH_2\) (\(n = 1\)), the hydrophobic part is a bit larger.
• For \(CH_3CH_2CH_2NH_2\) (\(n = 2\)), the hydrophobic part is larger.
• For \(CH_3CH_2CH_2CH_2NH_2\) (\(n = 3\)), the hydrophobic part is larger.
• For \(CH_3CH_2CH_2CH_2CH_2CH_2NH_2\) (\(n = 5\)), it has the longest hydrocarbon chain among the given options.

Answer:

C. \(CH_3CH_2CH_2CH_2CH_2CH_2NH_2\)