Textbook Question
a. Which of the following compounds can exist as cis–trans isomers?
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4. Alkanes and Cycloalkanes
Cis vs Trans
6:58 minutesProblem 72c
Textbook Question
Assign relative priorities to each set of substituents:
c. -C(=O)CH3, -CH=CH2, -Cl, -C=N
Verified step by step guidance1
Step 1: Understand the Cahn-Ingold-Prelog (CIP) priority rules. These rules are used to assign priorities based on atomic number, connectivity, and bonding. The higher the atomic number of the directly attached atom, the higher the priority. If the directly attached atoms are the same, move outward to the next set of atoms and compare.
Step 2: Analyze the substituents individually. For -C(=O)CH3, the carbon is double-bonded to oxygen, which has a higher atomic number than hydrogen or carbon. This increases its priority. For -CH=CH2, the carbon is double-bonded to another carbon, which is less electronegative than oxygen. For -Cl, chlorine has a high atomic number (17), giving it a high priority. For -C=N, the carbon is triple-bonded to nitrogen, which has an atomic number of 7, higher than carbon but lower than chlorine.
Step 3: Compare the substituents based on the atomic number of the directly attached atoms. Chlorine (-Cl) has the highest atomic number (17), so it will have the highest priority. Oxygen in -C(=O)CH3 has an atomic number of 8, which is higher than nitrogen in -C=N (atomic number 7) and carbon in -CH=CH2 (atomic number 6).
Step 4: Consider the bonding and connectivity for the remaining substituents. For -C(=O)CH3, the carbon is double-bonded to oxygen, which increases its priority over -C=N, where the carbon is triple-bonded to nitrogen. Finally, -CH=CH2 has the lowest priority because it is only bonded to carbons and hydrogens.
Step 5: Assign the relative priorities based on the analysis: 1) -Cl, 2) -C(=O)CH3, 3) -C=N, 4) -CH=CH2.
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Video duration:
6mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Substituent Priority in Organic Chemistry
In organic chemistry, substituents attached to a carbon chain can be prioritized based on their functional groups and the rules established by the Cahn-Ingold-Prelog (CIP) priority system. This system assigns higher priority to substituents based on atomic number and connectivity, which is crucial for determining stereochemistry and reactivity in organic compounds.
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Functional Groups
Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the context of the question, the substituents -C(=O)CH3 (an acyl group), -CH=CH2 (an alkene), -Cl (a halogen), and -C=N (a nitrile) represent different functional groups, each with distinct properties that influence their priority.
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Electronegativity and Reactivity
Electronegativity refers to the tendency of an atom to attract electrons in a bond. In assigning priorities to substituents, electronegativity plays a role, as more electronegative atoms (like Cl) can influence the reactivity and stability of the molecule. Understanding how electronegativity affects the behavior of substituents is essential for predicting the outcomes of chemical reactions.
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