VCAA Chemistry How are organic compounds categorised and synthesised?

Methyl pentanoate contains 6 carbons ($1$ from methyl + $5$ from pentanoate), whereas propyl butanoate contains 7 carbons ($3$ from propyl + $4$ from butanoate). Isomers must have the same molecular formula.

This name is invalid because a pentanoic acid chain only has 5 carbons, so a substituent cannot be at position 6. Furthermore, a methyl pentanoic acid derivative would only have 6 carbons total, not the required 7.

Although a structure constructed from this name would have 7 carbons, '3-propylbutanoic acid' is not a valid IUPAC name. The propyl group would extend the longest carbon chain, making the correct parent name hexanoic acid (specifically 3-methylhexanoic acid).

Esters cannot form intermolecular hydrogen bonds, resulting in weaker dipole-dipole interactions and a lower boiling point compared to alcohols and carboxylic acids.

While alcohols can form hydrogen bonds, they do not form stable dimers like carboxylic acids do, resulting in slightly weaker overall intermolecular forces and a lower boiling point than option B.

Amines can form hydrogen bonds, but because nitrogen is less electronegative than oxygen, the N-H bond is less polar than the O-H bond. This makes their hydrogen bonds weaker than those in alcohols and carboxylic acids.

This is a ketone (3-methyl-2-butanone). Acid-catalyzed hydration of alkenes produces alcohols, not carbonyl compounds; ketones are typically formed from the hydration of alkynes or oxidation of alcohols.

This is the anti-Markovnikov product (3-methyl-2-butanol). The reaction does not favor the formation of the less stable secondary carbocation intermediate required to produce this secondary alcohol.

This is a vicinal diol. Acid-catalyzed hydration adds water ($H-OH$) across the double bond to form a mono-alcohol, whereas diols are formed through oxidation reactions like dihydroxylation.

This is incorrect because there are more than 4 structural isomers. This answer likely misses one of the positional combinations of the halogens on the propane chain.

This is incorrect because it overcounts the number of structural isomers. There are exactly 5 unique positional combinations for one bromine and one chlorine atom on a propane chain.

This is incorrect because it overcounts the number of structural isomers. Stereoisomers (enantiomers) are not counted when specifically asking for structural isomers.

This formula is incorrect because a triglyceride must contain 6 oxygen atoms, not 3, and the carbon and hydrogen counts do not balance the transesterification reaction.

This formula is incorrect because it fails to account for the 3 carbon atoms from the glycerol backbone, resulting in 54 carbons instead of 57.

This formula is incorrect because a triglyceride contains 3 ester groups, meaning it must have 6 oxygen atoms, not 3.

Intramolecular forces hold atoms together within a molecule; boiling involves separating molecules from one another, not breaking bonds within them. Furthermore, alkanes do not contain the electronegative atoms necessary for hydrogen bonding.

Alkanes are nonpolar hydrocarbons that lack the hydrogen atoms bonded to highly electronegative atoms (N, O, F) required to form hydrogen bonds.

Dispersion forces are intermolecular (between molecules), not intramolecular. Intramolecular forces refer to the covalent bonds holding the carbon and hydrogen atoms together.

While using renewable materials is a core goal, the principles focus on minimizing waste (unwanted products) generated during the reaction, rather than minimizing reactants.

Green chemistry promotes the transition to renewable raw materials (such as agricultural products) rather than relying on depleting non-renewable resources like petroleum.

This option is incorrect because green chemistry aims to use renewable resources, and the primary objective regarding synthesis efficiency is the reduction of waste products.

The molecule $\text{CH}_2=\text{CBrCl}$ has two identical hydrogen atoms on one of the double-bonded carbons, which prevents cis-trans isomerism.

The molecule $\text{CH}_3\text{CHBrCl}$ is an alkane with only single bonds, so it cannot exhibit cis-trans isomerism (though it does have enantiomers).

The molecule $(\text{CH}_3)_2\text{C}=\text{CCl}_2$ has identical groups on both carbons of the double bond (two methyls on one, two chlorines on the other), making cis-trans isomerism impossible.

Chemical reactivity refers to the stability of the molecule against chemical changes, whereas the melting point is a physical property determined by the strength of intermolecular forces.

The strength of covalent bonds determines the polymer's thermal stability (resistance to decomposition), but the melting point is governed by the intermolecular forces holding separate chains together.

Melting involves overcoming forces between different polymer chains (intermolecular), whereas interactions between atoms within the same chain (intramolecular) determine the chain's structure and stiffness.

Butanone ($C_4H_8O$) has a longer carbon chain than propanone, leading to stronger London dispersion forces and a higher boiling point.

Hexanone ($C_6H_{12}O$) has the highest molecular weight and longest carbon chain among the options, resulting in the strongest intermolecular forces and the highest boiling point.

Pentanone ($C_5H_{10}O$) has a larger molecular size than propanone, which results in stronger intermolecular attractions and a higher boiling point.

Oxidation involves the loss of electrons or the addition of oxygen to a molecule. It is not the reaction mechanism used for exchanging ester groups between triglycerides and alcohols.

While the underlying mechanism is a nucleophilic acyl substitution, this is a broad category. The specific term for the reaction between an ester and an alcohol is transesterification.

Saponification is the base-catalyzed hydrolysis of triglycerides to produce glycerol and fatty acid salts (soap), rather than the reaction involving methanol to exchange ester groups.

Since structural isomers share the same molecular formula, they contain the exact same number of atoms of each element and therefore have identical molar masses.

Molecular mass is determined by the sum of the atomic masses in the molecular formula; since isomers have the same formula, their molecular masses are the same.

The empirical formula represents the simplest ratio of elements; because the molecular formula is identical for isomers, their empirical formulas are also identical.