Cách xác định độ ưu tiên nhóm thế || Quy tắc Cahn-Ingold-Prelog || Cahn-Ingold-Prelog priority rules

HHB EDUCATION CHANNEL

10 May 202012:37

Summary

TLDRThis educational video script discusses the Cahn-Ingold-Prelog priority rules, crucial for determining the priority of atoms or groups in organic compounds. It explains how these rules help in identifying the RS configuration for optical isomers and the AS configuration for geometric isomers. The script outlines four key rules for establishing the priority order: considering atomic numbers from the periodic table, comparing subsequent atomic levels if necessary, accounting for multiple bonds, and evaluating the bulkiness of substituents. Examples, such as ethanol and butan-2-ol, illustrate these principles, providing a clear foundation for understanding stereochemistry.

Takeaways

🔍 The video discusses the application of Cahn-Ingold-Prelog (CIP) rules for determining the priority of atoms or groups of atoms in organic compounds.
🧪 The priority order helps in determining the configuration of chiral centers in organic molecules, which is crucial for understanding stereochemistry.
📚 The first rule of CIP is based on the atomic number of the first atom directly bonded to the chiral carbon, with higher atomic numbers having higher priority.
🔢 If the first atoms of two groups are of the same element, the rule extends to the next atom in the substituent until a difference is found.
⚖️ Rule two involves comparing the atomic numbers of the next atoms in the substituents if the first atoms are of equal priority.
🔄 The process of comparing atomic numbers continues down the substituents until a higher priority is established.
🔗 Rule three addresses the situation where substituents contain multiple bonds, effectively counting double or triple bonds as two or three single bonds for comparison purposes.
🌐 Rule four is used to compare substituents with identical atoms but different connectivity, such as a double bond versus a single bond.
📈 The script provides examples of how to apply these rules to determine the relative priorities of different substituents in organic molecules.
🎓 The video concludes by emphasizing the importance of understanding CIP rules for students studying organic chemistry, as it lays the foundation for determining the stereochemistry of molecules.

Q & A

What is the Cahn-Ingold-Prelog priority rules?
-The Cahn-Ingold-Prelog priority rules are used to determine the priority of atoms or groups of atoms in organic compounds, which helps in determining the configuration of chiral centers.
How do you determine the priority of different groups attached to an asymmetric carbon atom?
-The priority is determined by the atomic number of the first atom directly attached to the asymmetric carbon. If the atomic numbers are the same, you move to the next atom in the group and compare their atomic numbers.
What is the first rule in the Cahn-Ingold-Prelog priority rules?
-The first rule states that the group with the highest atomic number of the first atom directly attached to the chiral carbon gets the highest priority.
How do you handle situations where the first atoms of the groups have the same atomic number?
-If the first atoms have the same atomic number, you move to the next atoms in each group and compare their atomic numbers until you find a difference to determine the priority.
What happens if all atoms in a group have the same atomic numbers?
-If all atoms in a group have the same atomic numbers, you consider the total atomic number of the group, but the priority is determined by the first pair of atoms with different atomic numbers.
Can you give an example of how to apply the Cahn-Ingold-Prelog rules?
-In the example of ethanol, the four groups attached to the chiral carbon are -OH, -NH2, -CH3, and -H. The -OH group has the highest priority due to the oxygen atom, followed by -NH2, then -CH3, and -H has the lowest priority.
What is the significance of the Cahn-Ingold-Prelog rules in stereochemistry?
-The Cahn-Ingold-Prelog rules are fundamental in stereochemistry as they allow chemists to determine the R or S configuration of chiral centers, which is crucial for understanding the three-dimensional structure of molecules.
How do the Cahn-Ingold-Prelog rules apply to groups with multiple bonds?
-For groups with multiple bonds, each multiple bond is considered as two or three single bonds to the same atom when determining priority.
What is the fourth rule of the Cahn-Ingold-Prelog priority rules?
-The fourth rule states that if substituents have the same atomic number, the one with the lower sum of atomic numbers of all atoms in the substituent has the higher priority.
Can you provide a practical application of the Cahn-Ingold-Prelog rules?
-These rules are used in organic chemistry to name stereoisomers, determine the absolute configuration of molecules, and predict the outcome of reactions involving chiral molecules.
How do the Cahn-Ingold-Prelog rules help in understanding the structure of organic compounds?
-By assigning priorities to groups attached to chiral centers, the Cahn-Ingold-Prelog rules help in assigning the R or S configuration, which is essential for understanding the spatial arrangement of atoms in organic compounds.

Outlines

00:00

🔍 Introduction to Cahn-Ingold-Prelog Rules

The paragraph introduces the Cahn-Ingold-Prelog (CIP) priority rules, which are used to determine the priority of atoms or groups of atoms in organic compounds. This priority is essential for defining the RS configuration of chiral molecules and the AS configuration in stereochemistry. The script explains that in organic compounds, four different groups are connected to a carbon atom, and the CIP rules help to determine the configuration at that carbon. The first rule is based on the atomic numbers of the atoms in the first group directly connected to the carbon. The higher the atomic number, the higher the priority. An example using ethanol is provided, where the four groups connected to the carbon are analyzed based on the atomic numbers of the first atoms in each group. Hydrogen is noted to generally have the lowest priority due to its atomic number being 1.

05:01

📚 Applying CIP Rules for Group Prioritization

This paragraph delves deeper into applying the CIP rules to determine the priority of groups. It explains that if the first atoms in two groups have the same atomic number, one must look at the next atoms in each group connected to the first. The process is repeated until the priority can be established. An example with butan-2-ol is given, where the priority of the CH3 and CH2CH3 groups is determined by examining the next atoms connected to the carbons in these groups. The script also explains that if the first atoms of two groups are the same, one compares the next atoms in sequence until a difference is found. The group with the higher atomic number wins priority. Another example with 3,3-dimethylbutan-1,2-diol is used to illustrate the application of these rules.

10:03

🔬 Advanced CIP Rule Application

The final paragraph discusses the application of the CIP rules in more complex scenarios, such as when dealing with groups that have double or triple bonds. The rule states that if a group has a double or triple bond with another atom, it is treated as having two or three single bonds for the purpose of determining priority. The script uses the example of a group with a double bond between carbon and oxygen, where the carbon is considered to have two single bonds with oxygen and vice versa. The paragraph concludes with an example comparing the priority of two groups, CH2OH and CH3, based on these rules. It also introduces the fourth rule, which is used to determine the priority of isotopes or groups with different masses. The example given involves comparing different hydrogen isotopes based on their mass numbers.

Mindmap

Keywords

💡Cahn-Ingold-Prelog priority rules

The Cahn-Ingold-Prelog priority rules, often abbreviated as CIP rules, are a set of principles used in organic chemistry to determine the relative priority of different substituents attached to a stereocenter. In the video, these rules are central to the theme as they are used to establish the configuration of chiral centers in organic compounds, which is crucial for understanding the spatial arrangement of molecules and their properties.

💡Stereochemistry

Stereochemistry is the study of the three-dimensional arrangement of atoms in molecules. It is a key concept in the video as it relates to the configuration of molecules, which is determined using the CIP rules. The video discusses how stereochemistry influences the properties and reactivity of molecules, particularly in the context of chiral compounds.

💡Chiral center

A chiral center is a carbon atom bonded to four different groups, which gives rise to stereoisomers. The video script explains how to determine the configuration of chiral centers using the CIP rules, which is essential for understanding the properties of chiral molecules, such as their interactions with other substances and their biological activities.

💡RS configuration

RS configuration refers to the absolute configuration of a chiral center, where 'R' stands for rectus (right) and 'S' stands for sinister (left). The video explains how to determine the RS configuration using the CIP rules, which is important for identifying the spatial arrangement of atoms around a chiral center and is critical in fields such as drug development and chemistry.

💡Atomic number

The atomic number is the number of protons in the nucleus of an atom, which determines the element's position in the periodic table. In the context of the video, atomic numbers are used to assign priority to different substituents in the CIP rules, with higher atomic numbers indicating higher priority.

💡Substituent

A substituent is a group of atoms that replaces one or more hydrogen atoms in a molecule. The video discusses how to determine the priority of substituents using the CIP rules, which is essential for establishing the stereochemistry of molecules and understanding their physical and chemical properties.

💡Hydrogen

Hydrogen is the first and simplest element in the periodic table. In the video, it is mentioned that hydrogen typically has the lowest priority in the CIP rules, as it has the smallest atomic number. This is important for determining the configuration of chiral centers in organic compounds.

💡Ethanol

Ethanol is an organic compound with the formula C2H5OH. The video uses ethanol as an example to illustrate how to apply the CIP rules to determine the priority of substituents and the configuration of chiral centers in organic molecules.

💡Butan-2-ol

Butan-2-ol is a specific isomer of butanol, an alcohol with a four-carbon chain. The video script uses the structure of butan-2-ol to demonstrate how to apply the CIP rules to determine the relative priorities of substituents and the stereochemistry of the molecule.

💡Pentavalent

Pentavalent refers to an atom that can form five bonds, such as nitrogen in certain compounds. The video mentions pentavalent atoms in the context of determining substituent priorities using the CIP rules, which is important for understanding the stereochemistry of molecules with such atoms.

💡Tetrahedral

Tetrahedral refers to a geometric shape with four points, often used to describe the spatial arrangement of atoms around a central atom in organic chemistry. The video discusses the tetrahedral geometry of chiral centers and how the CIP rules apply to such structures to determine the stereochemistry of molecules.

Highlights

Introduction to the Cahn-Ingold-Prelog priority rules for determining the priority of atoms or groups in organic compounds.

Explanation of how the priority order can be used to determine the RS configuration in optical isomers and the AS configuration in geometrical isomers.

Description of the first rule: Priority is determined by the atomic number of the first atom directly bonded to the asymmetric carbon.

Example using ethanol to illustrate the application of the first rule to determine the priority of different groups.

Clarification that hydrogen typically has the lowest priority due to its atomic number.

Introduction to the second rule: If the first atoms of two groups are the same, consider the next atom in each group.

Example using butan-2-ol to demonstrate the application of the second rule to resolve priority between two groups.

Explanation of how to compare atoms in pairs to determine the priority of groups.

Discussion on the importance of not considering the total atomic number but focusing on the first differing pair.

Introduction to the third rule: If a group has a double or triple bond, it is considered as two or three single bonds for priority purposes.

Example using 3,3-dimethylbutan-1,2-diol to show how the third rule is applied to determine group priority.

Emphasis on not needing to consider the total sum of atomic numbers when comparing groups.

Introduction to the fourth rule: The size of the substituent group is considered for determining priority.

Example comparing different hydrogen atoms to illustrate the fourth rule's application.

Conclusion summarizing the importance of the Cahn-Ingold-Prelog rules in determining the configuration of organic compounds.

Closing remarks wishing success to the viewers and looking forward to future encounters.