Avoid These 3 CIP-Rules Mistakes! ❌✅ Chemistry Tutorial English

Summary

This video breaks down key principles of the Zaitsev nomenclature, focusing on how to assign priorities to substituents and the nuances in determining R/S configurations. It emphasizes rules that often confuse students, such as handling double bonds, prioritizing atoms in molecules like cine, and correctly drawing molecular structures for easy configuration determination. The video offers practical insights for mastering the complex aspects of organic chemistry, including step-by-step guidance for assigning priorities and drawing clear, unambiguous molecular structures.

Takeaways

• 😀 Prioritize substituents based on the nuclear mass of atoms for correct CIP nomenclature.
• 😀 If the lowest-priority substituent points away from you, assign the R or S configuration based on the clockwise or counterclockwise arrangement of the other substituents.
• 😀 When the lowest-priority substituent points towards you, imagine or redraw the molecule to reverse the R/S configuration.
• 😀 Double bonds are treated as two single bonds in the CIP system, which helps in assigning priorities more accurately.
• 😀 Redrawing molecules with double bonds as if they were single bonds can clarify the priority assignment between atoms.
• 😀 Don't add up the values of substituents; instead, compare individual atoms with the highest nuclear mass to determine priorities.
• 😀 In cases of ties between atoms, follow the branches with the highest priority atoms and continue the comparison.
• 😀 For molecules with multiple oxygen or sulfur substituents, compare their nuclear masses directly in a duel format to assign priorities.
• 😀 Correct molecular drawing is essential for accurate configuration determination; make sure wedges are drawn in the same direction.
• 😀 Drawing all bonds into one consistent direction (both up or both down) avoids confusion when assigning configurations.
• 😀 Following these detailed rules improves understanding of stereochemistry and reduces common mistakes in complex molecules like cine.

Q & A

What is the principle behind assigning priorities in the Z-configurations?

Priorities are assigned to substituents based on the nuclear mass of each atom bound to the substituent. The higher the mass, the higher the priority. This helps determine the R or S configuration.

What happens when the lowest priority substituent points towards the observer?

When the lowest priority substituent points towards the observer, you need to reverse the R and S assignments. This means that if the arrangement is clockwise, it becomes S, and if counterclockwise, it becomes R.

How are double bonds treated in the Z-nomenclature?

Double bonds are treated as two single bonds. This means a molecule with a double bond can be redrawn as if it has two single bonds to assign priorities, which helps in determining the configuration.

What is the correct way to handle a molecule with a double bond when assigning priorities?

You should redraw the molecule considering the double bond as two single bonds, making it easier to compare the priority of each substituent.

Why is determining priority sometimes challenging for molecules like cine?

Molecules like cine are challenging because students often wrongly add up the values of substituents. The correct approach is to perform a duel between the highest nuclear mass atoms on each side and assign the priorities based on these duels.

What does the concept of 'duels' between atoms in determining priorities mean?

The concept of 'duels' refers to comparing the highest mass atoms on each side of a substituent. If one atom wins a duel, the side with that atom gets a higher priority. This process is continued until a clear priority can be determined.

How should you deal with tied substituents when assigning priorities?

When substituents tie, you continue comparing along the chain, considering the next atoms with the highest atomic mass, and resolve the ties by following these steps.

What common mistake do students make when assigning priority in the example with sulfur and oxygen?

The common mistake is to wrongly add the values of the substituents like oxygen and sulfur. The correct method is to perform a duel between the highest nuclear mass atoms—sulfur wins over oxygen in this case.

What is the importance of drawing molecules properly when determining their configuration?

Properly drawing molecules is crucial because incorrect drawing can lead to confusion in determining the configuration. For example, if wedges do not align in the same direction, it becomes difficult to assign the correct R or S configuration.

How should wedges be drawn to avoid confusion in determining molecular configuration?

Both wedges should be drawn in the same direction (either both up or both down) while the other bonds are drawn in the opposite direction. This unambiguous drawing simplifies the correct determination of the configuration.