Quiz - Carbon-Carbon Bond Formation - 1 | Carbon-Carbon Bond Formation

Organic Chemistry 3 - Quiz - Carbon-Carbon Bond Formation - 1


Which of the following best describes the role of palladium in the Heck reaction?

Palladium serves as a catalyst in the Heck reaction by forming a complex with the alkyl halide and the alkene, leading to oxidative addition, insertion, and reductive elimination steps, which together facilitate the formation of a carbon-carbon σ bond.


Which reagents are typically used in the Suzuki reaction to couple aryl halides with organoboranes?

The Suzuki reaction generally employs a palladium catalyst along with a base. Organoboranes are coupled with aryl halides to form a new carbon-carbon bond, typically using a palladium catalyst like Pd(PPh3)4 and a base (e.g., NaOH, K2CO3).


What distinguishes the Sonogashira coupling from other palladium-catalyzed reactions?

The Sonogashira coupling is characterized by the use of both a palladium catalyst and a copper co-catalyst. This reaction uniquely couples aryl or vinyl halides with terminal alkynes under relatively mild conditions to form substituted alkynes.


The Simmons-Smith reaction involves the creation of cyclopropanes from alkenes. What is the intermediate involved in this process?

In the Simmons-Smith reaction, a carbenoid intermediate is involved, which is generated from diiodomethane (CH2I2) and a zinc-copper couple. The carbenoid then inserts into the double bond of an alkene to form a cyclopropane ring.


In olefin metathesis, what kind of catalytic species is responsible for the bond reorganization?

Olefin metathesis is a reaction in which the bonds of two alkenes are broken and reformed to create two new alkenes. It is catalyzed by a transition metal carbene complex, such as those derived from molybdenum or ruthenium.


When synthesizing organocuprates, the initial step typically involves:

In the formation of organocuprates (Gilman reagents), a transmetalation step is crucial, where an organolithium compound reacts with a copper(I) salt, transferring the organic group to copper, resulting in a copper(I) organocuprate.


Carbenes, which are neutral species with a divalent carbon atom, display a wide range of reactivities. Their reactive nature is primarily due to:

Carbenes are highly reactive due to the divalent carbon's lack of a complete octet, which makes them electrophilic. This electrophilic nature allows carbenes to insert into C-H bonds, add to double bonds, and participate in various other reactions.


Coupling reactions often require the use of transition metals. What role do these metals predominantly play?

Transition metals are widely utilized in coupling reactions as redox catalysts. They facilitate the transfer of electrons in oxidative addition and reductive elimination steps, allowing the coupling of two organic fragments.


In the context of organometallic chemistry, what is the significance of the oxidative addition step?

Oxidative addition is a crucial step in many catalytic cycles, including coupling reactions, wherein the metal engages with a substrate (typically a halogenated organic molecule), causing the metal's coordination number and oxidation state to increase.


In terms of regioselectivity, how do Heck-type reactions compare to hydroboration of alkenes?

Hydroboration is an anti-Markovnikov selective reaction, adding boron to the less substituted carbon of the double bond. In contrast, Heck reactions are usually not explicitly concerned with Markovnikov or anti-Markovnikov selectivity.