Question 1

Regarding the IUPAC naming and physical properties of aldehydes, which of the following statements is true?

Accepted Answer

The IUPAC name for a three-carbon aldehyde is propanal, and it generally has a lower boiling point than its corresponding alcohol, propan-1-ol.

Answer

The suffix for aldehydes is -oic acid, and the carbonyl carbon is always assigned the highest possible number in the chain.

Answer

The IUPAC name for a three-carbon aldehyde is propanone, and it can form strong intermolecular hydrogen bonds with other aldehyde molecules.

Answer

Aldehydes are named using the suffix -ol, and they are completely insoluble in water regardless of the carbon chain length.

Question 2

Which of the following describes the solubility of aldehydes in water and the reasoning behind it?

Accepted Answer

Short-chain aldehydes like ethanal are soluble in water because they can form hydrogen bonds with water molecules.

Answer

Aldehydes become more soluble in water as the length of the non-polar hydrocarbon chain increases.

Answer

Aldehydes are completely insoluble in water because they cannot form any hydrogen bonds with water.

Answer

Aldehydes are only soluble in water if they contain at least ten carbon atoms to offset the polarity of the carbonyl group.

Question 3

What is the correct IUPAC name for an aldehyde with a five-carbon straight chain where there is a methyl substituent located on the third carbon?

Accepted Answer

3-methylpentanal

Answer

3-methylpentan-1-one

Answer

3-methylbutanol

Answer

2-methylpentanal

Question 4

Which of the following explains why the boiling point of methanal (

HCHO

) is significantly higher than that of ethane (

CH_{3}CH_{3}

), even though they have similar molar masses?

Accepted Answer

The polar carbonyl group in methanal creates permanent dipole-dipole attractions, which are stronger than the London dispersion forces in ethane.

Answer

The covalent bonds within an ethane molecule are much weaker than those in a methanal molecule, resulting in a lower boiling point.

Answer

Methanal is a non-polar molecule, which leads to increased surface area contact compared to ethane.

Answer

Methanal molecules form strong intermolecular hydrogen bonds with each other, whereas ethane molecules do not.

Question 5

Which of the following describes the bonding in the aldehyde functional group and its effect on the molecule's reactivity?

Accepted Answer

The

HCHO

bond is polar with a partial positive charge on the carbon atom, making it susceptible to attack by nucleophiles.

Answer

The oxygen atom carries a partial positive charge, which attracts electrophiles to the carbon atom.

Answer

The bond between carbon and oxygen is a triple bond, which requires high energy to break during substitution reactions.

Answer

The

HCHO

bond is non-polar because carbon and oxygen have similar electronegativities, making the molecule chemically inert.

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