Textbook Question
Show how you might synthesize the following compounds starting with bromobenzene, and alkyl or alkenyl halides of four carbon atoms or fewer.
a. 3-phenylprop-1-ene
13. Alcohols and Carbonyl Compounds
Organometallic Cumulative Practice
8:03 minutesProblem 45a
Textbook Question
Metathesis of which of the following sets of alkenes leads to the highest yield of a single alkene?
1. 1-butene and 1-pentene
2. 2-butene and 3-hexene
3. 2-butene and 1-pentene
Verified step by step guidance1
Step 1: Understand the concept of alkene metathesis. Alkene metathesis is a reaction where two alkenes exchange their alkylidene groups, forming new alkenes. The reaction is catalyzed by metal carbene complexes, and the product distribution depends on the stability and symmetry of the resulting alkenes.
Step 2: Analyze the given sets of alkenes. For each pair, consider the possible products of the metathesis reaction. The reaction involves breaking the double bonds of the alkenes and recombining the fragments to form new alkenes.
Step 3: Evaluate the stability of the potential products. The highest yield of a single alkene is achieved when the reaction favors the formation of a single, thermodynamically stable product. Symmetry and substitution patterns of the alkenes play a key role in determining the product distribution.
Step 4: For each pair of alkenes: (1) 1-butene and 1-pentene, (2) 2-butene and 3-hexene, and (3) 2-butene and 1-pentene, write the possible products of the metathesis reaction. Consider the substitution patterns of the resulting alkenes and their relative stabilities (e.g., more substituted alkenes are generally more stable).
Step 5: Compare the product distributions for each pair. Identify the pair that leads to the formation of a single, stable alkene as the major product. This pair will correspond to the highest yield of a single alkene.
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Video duration:
8mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Alkene Metathesis
Alkene metathesis is a chemical reaction that involves the exchange of alkyl groups between alkenes, leading to the formation of new alkenes. This reaction is facilitated by catalysts, such as those based on molybdenum or tungsten, and is significant in organic synthesis for producing higher-value compounds. Understanding the mechanism and factors influencing the reaction is crucial for predicting the outcomes of different alkene combinations.
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Thermodynamic Stability of Alkenes
The stability of alkenes is influenced by their degree of substitution; more substituted alkenes are generally more stable due to hyperconjugation and the inductive effect. In metathesis, the formation of more stable alkenes typically leads to higher yields. Recognizing the stability of the potential products formed from the metathesis reaction helps in determining which alkene pair will yield the most favorable outcome.
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04:28Understanding trends of alkene stability.
Selectivity in Metathesis Reactions
Selectivity in metathesis reactions refers to the preference for forming certain products over others based on the starting materials. Factors such as sterics, electronic effects, and the nature of the catalyst can influence selectivity. Analyzing the structure of the alkenes involved allows chemists to predict which combinations will yield a single, predominant alkene, thus maximizing the efficiency of the reaction.
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