Optical Isomerism and Optical Activity Quiz

In the Marvel Universe, Mrs. Avis and Dylan are in Tony Stark’s lab, discussing why some molecules have the superpower to rotate plane-polarized light. What gives rise to optical isomerism in molecules with a single chiral centre?

• Presence of a double bond

• Chirality in molecules with a single chiral centre

• Presence of a benzene ring

• High molecular weight

Answer explanation

Optical isomerism arises from chirality, which occurs in molecules with a single chiral centre. This chiral centre creates non-superimposable mirror images, leading to different optical isomers.

During a chemistry experiment, Mr.Subash and Lisa are studying molecules with asymmetric carbon atoms. What is a characteristic of optical isomers in such molecules?

• They are always superimposable

• They are object and nonsuperimposable

• They have identical physical properties

• They do not rotate plane-polarised light

Answer explanation

Optical isomers, or enantiomers, are non-superimposable mirror images of each other due to the presence of asymmetric carbon atoms. This characteristic distinguishes them from identical objects, making the correct choice 'They are object and nonsuperimposable'.

In their chemistry lab, EeFan and Lisa mix equal amounts of two enantiomers. What type of mixture have they created?

• A mixture containing only one enantiomer

• A mixture containing equal amounts of two enantiomers

• A mixture of different elements

• A mixture that is optically active

Answer explanation

A racemic mixture consists of equal amounts of two enantiomers, which are mirror-image forms of a chiral molecule. This balance results in no net optical activity, distinguishing it from mixtures with only one enantiomer.

EeTeng and Aliya are investigating a chemical reaction in their organic chemistry lab. They measure the optical activity of both the reactants and the products. How can this data be used in organic chemistry?

• To determine the boiling point of a compound

• As evidence for SN1 and SN2 mechanisms

• To measure the density of a solution

• To identify the color of a compound

Answer explanation

Data on optical activity helps distinguish between reactants and products in reactions, providing evidence for SN1 and SN2 mechanisms by showing changes in chirality and rotation, which are key in understanding these pathways.

During a chemistry class, Aliya and Mayuha are discussing different types of isomers. Mr.MatthewBrown asks, "Geometric isomers are a subtype of which broader class of isomers?" What should Mayuha answer?

• Structural isomers

• Stereoisomers

• Functional isomers

• Chain isomers

Answer explanation

Geometric isomers are a type of stereoisomers, which differ in the spatial arrangement of atoms. Stereoisomers include both geometric and optical isomers, making 'stereoisomers' the correct broader class for geometric isomers.

Joshua and Mayuha each build a model of a molecule. Both models have atoms joined in the same order, but the arrangement of the atoms in space is different. Which statement best describes the relationship between their models?

• Atoms are joined in the same order but have a different arrangement in space.

• Atoms are joined in a different order but have the same arrangement in space.

• Atoms are joined in the same order and have the same arrangement in space.

• Atoms are joined in a different order and have a different arrangement in space.

Answer explanation

Stereoisomers have the same connectivity of atoms but differ in their spatial arrangement. This is why the correct statement is that atoms are joined in the same order but have a different arrangement in space.

During a chemistry study session, Joshua and Lisa are discussing different types of isomerism. Which of the following is a type of structural isomerism?

• Geometric isomerism

• Optical isomerism

• Chain isomerism

• Stereoisomerism

Answer explanation

Chain isomerism is a type of structural isomerism where compounds have the same molecular formula but different arrangements of the carbon skeleton. Geometric and optical isomerism are types of stereoisomerism, not structural.

During a chemistry discussion, Joshua claims that geometric isomerism and optical isomerism are both types of stereoisomerism. Aliya is unsure if this is correct. Is Joshua's claim correct? Justify your answer using the classification of isomerism.

• Yes, both are subtypes of stereoisomerism.

• No, only geometric isomerism is a subtype of stereoisomerism.

• No, only optical isomerism is a subtype of stereoisomerism.

• No, neither is a subtype of stereoisomerism.

Answer explanation

Yes, both geometric isomerism and optical isomerism are types of stereoisomerism. Stereoisomerism involves isomers with the same molecular formula and connectivity but different spatial arrangements, which includes both types.

Mrs.Avis and Joshua each have a pair of gloves. Mrs.Avis's gloves are left and right-handed, and Joshua's gloves are also left and right-handed, but the two pairs are mirror images of each other and cannot be superimposed. What type of isomers do Mrs.Avis and Joshua's gloves represent?

• Molecules with the same molecular formula but different connectivity of atoms

• Molecules that are mirror images of each other and cannot be superimposed

• Molecules with the same structure but different physical states

• Molecules that have the same boiling point but different melting points

Answer explanation

Optical isomers, also known as enantiomers, are molecules that are non-superimposable mirror images of each other. This characteristic distinguishes them from other types of isomers, making the correct choice the second option.

During a chemistry lab, Lisa and Charles are investigating different types of nucleophilic substitution reactions. What type of evidence is often used to distinguish between S_N1 and S_N2 reactions?

• Color change during the reaction

• Formation of optical isomers

• Change in temperature

• Change in pressure

Answer explanation

The formation of optical isomers is key in distinguishing S_N1 and S_N2 reactions. S_N1 reactions can lead to racemic mixtures due to carbocation formation, while S_N2 reactions result in inversion of configuration, producing optical isomers.