The boiling points of hex-1-ene (64 °C) and hex-1-yne (71 °C) are sufficiently close that it is difficult to achieve a clean separation by distillation. Show how you might use the acidity of hex-1-yne to remove the last trace of it from a sample of hex-1-ene.

검증된 단계별 안내

Identify the structural difference between hex-1-ene and hex-1-yne. Hex-1-ene is an alkene with a double bond, while hex-1-yne is an alkyne with a triple bond.

Understand the acidity of alkynes. Terminal alkynes like hex-1-yne have acidic hydrogen atoms due to the sp hybridization of the carbon atom bonded to hydrogen, making them more acidic than alkenes.

Consider using a strong base to deprotonate hex-1-yne. A strong base such as sodium amide (NaNH₂) can be used to remove the acidic hydrogen from the terminal alkyne, forming a sodium acetylide.

Recognize that the sodium acetylide formed is a salt and is soluble in polar solvents like water, whereas hex-1-ene remains nonpolar and insoluble in water.

Separate the mixture by adding water to dissolve the sodium acetylide, leaving hex-1-ene as the nonpolar residue. This exploits the difference in solubility to achieve separation.

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주요 개념

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Acidity of Alkynes

Alkynes, such as hex-1-yne, are more acidic than alkenes due to the sp-hybridized carbon atom, which holds the negative charge more stably when a hydrogen is removed. This acidity allows alkynes to react with strong bases, forming acetylide ions, which can be exploited for separation purposes.

Distillation

Distillation is a separation technique that relies on differences in boiling points to separate components of a mixture. When the boiling points are close, as with hex-1-ene and hex-1-yne, achieving a clean separation becomes challenging, necessitating alternative methods such as chemical reactivity differences.

Chemical Reactivity for Separation

Using chemical reactivity differences, such as the acidity of hex-1-yne, can aid in separation. By treating the mixture with a strong base, hex-1-yne can be selectively deprotonated to form a salt, which can then be removed, leaving behind hex-1-ene. This method leverages the unique chemical properties of the components for effective separation.