Cyclohexane Conformations and Substituents

This episode of Crash Course Organic Chemistry explores the prevalence of hexagons in nature and their significance in chemistry, particularly in cyclohexane molecules. It covers the naming conventions for cycloalkanes, the concept of ring strain, and how it is measured using bomb calorimetry. The video delves into the conformations of cyclohexane, including the chair and boat forms, and provides guidance on drawing these structures. It also explains the importance of converting flat structures to chair drawings, emphasizing the stability of equatorial positions for bulky substituents.

What common shape is found in both natural and synthetic structures, including cyclohexane?

• Triangles

• Squares

• Hexagons

• Pentagons

What prefix is used in naming cycloalkanes to indicate substituents on the same face of the ring?

• Trans-

• Iso-

• Cis-

• Anti-

What instrument is used to measure the heat released during the combustion of cycloalkanes?

• Thermometer

• Bomb calorimeter

• Spectrometer

• Barometer

Which conformation of cyclohexane is considered the most stable due to staggered hydrogens and ideal bond angles?

• Chair

• Envelope

• Twist

• Boat

What happens to axial and equatorial positions during a chair flip in cyclohexane?

• No change occurs

• Only equatorial positions change

• Axial positions become equatorial and vice versa

• Only axial positions change

Why is the equatorial position preferred for bulky substituents in cyclohexane?

• It decreases molecular weight

• It increases angular strain

• It maximizes torsional strain

• It minimizes steric hindrance

What is the main reason for practicing drawing cyclohexane chair conformations?

• To improve artistic skills

• To memorize chemical formulas

• To understand molecular vibrations

• To visualize substituent positions and stability

In a flat cyclohexane structure, what does a solid wedge indicate about a substituent's position?

• It is not part of the molecule

• It is above the plane

• It is below the plane

• It is in the plane

What is the effect of diaxial strain in cyclohexane conformations?

• It reduces molecular weight

• It causes steric hindrance

• It increases bond angles

• It stabilizes the molecule

What is the preferred conformation for a tert-butyl group in cyclohexane?

• Axial

• Planar

• Twist

• Equatorial