Skip to main content
Ch.4 - The Study of Chemical Reactions
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoWade 9th EditionCh.4 - The Study of Chemical ReactionsProblema 22b
Capitolo 4, Problema 22b

Alkoxy radicals (R—O•) are generally more stable than alkyl (R•) radicals. Write an equation showing an alkyl free radical (from burning gasoline) abstracting a ­hydrogen atom from tert-butyl alcohol, (CH3)3COH. Explain why tert-butyl alcohol works as an antiknock additive for gasoline

Guida verificata passo dopo passo
1
Write the chemical equation for the reaction: An alkyl radical (R•) abstracts a hydrogen atom from tert-butyl alcohol ((CH₃)₃COH). The reaction can be represented as: R• + (CH₃)₃COH → RH + (CH₃)₃CO•. Here, the alkyl radical (R•) reacts with tert-butyl alcohol, resulting in the formation of an alkane (RH) and a tert-butoxy radical ((CH₃)₃CO•).
Explain the stability of the tert-butoxy radical ((CH₃)₃CO•): The alkoxy radical is stabilized by resonance and the electron-donating inductive effects of the three methyl groups attached to the central carbon. This makes the tert-butoxy radical more stable than the alkyl radical (R•).
Discuss the role of tert-butyl alcohol as an antiknock additive: In gasoline combustion, knocking occurs due to uncontrolled chain reactions involving free radicals. Tert-butyl alcohol acts as a radical scavenger by donating a hydrogen atom to alkyl radicals, forming a more stable alkoxy radical ((CH₃)₃CO•). This interrupts the chain reaction and reduces knocking.
Highlight the importance of hydrogen abstraction: The ability of tert-butyl alcohol to donate a hydrogen atom to alkyl radicals is key to its function as an antiknock additive. The resulting tert-butoxy radical is less reactive and does not propagate the chain reaction, thereby stabilizing the combustion process.
Summarize the benefits of tert-butyl alcohol in gasoline: By reducing knocking, tert-butyl alcohol improves engine performance and efficiency. Its ability to stabilize free radicals makes it an effective additive for smoother combustion.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.
Durata del video:
4m

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Radical Stability

Radical stability refers to the relative stability of free radicals, which are species with unpaired electrons. Alkoxy radicals (R—O•) are generally more stable than alkyl radicals (R•) due to the presence of the electronegative oxygen atom, which can delocalize the unpaired electron through resonance. This stabilization makes alkoxy radicals less reactive compared to their alkyl counterparts, influencing their behavior in chemical reactions.
Video consigliato:
03:43
The radical stability trend.

Hydrogen Abstraction

Hydrogen abstraction is a fundamental reaction mechanism in organic chemistry where a radical species removes a hydrogen atom from a molecule, resulting in the formation of a new radical and a stable molecule. In the context of the question, an alkyl radical from burning gasoline abstracts a hydrogen atom from tert-butyl alcohol, leading to the generation of a new radical and a more stable product. This process is crucial in combustion and radical chain reactions.
Video consigliato:
00:48
The definition of hydrogenation.

Antiknock Agents

Antiknock agents are additives used in gasoline to prevent engine knocking, which is the premature ignition of the fuel-air mixture in an engine cylinder. Tert-butyl alcohol acts as an antiknock additive because its structure allows for better combustion characteristics and reduces the formation of harmful radicals during combustion. This leads to smoother engine operation and improved performance by enhancing the octane rating of the fuel.
Video consigliato:
09:28
Reducing Agents
Pratica correlata
Domanda del libro di testo

In the presence of a small amount of bromine, cyclohexene undergoes the following light-promoted reaction:

b. Draw the structure of the rate-limiting transition state.

c. Use Hammond's postulate to predict which intermediate most closely resembles this transition state.

964
views
Domanda del libro di testo

Classify each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).

a. butane

b. isobutane

1377
views
Domanda del libro di testo

Use the information in Table 4-2 to explain why toluene (PhCH3) has a very high octane rating of 111. Write an equation to show how toluene reacts with an alkyl free radical to give a relatively stable radical.

1374
views
Domanda del libro di testo

In the presence of a small amount of bromine, cyclohexene undergoes the following light-promoted reaction:

a. Propose a mechanism for this reaction.

4927
views
Domanda del libro di testo

Classify each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).

c. 2-methylbutane

d. cyclohexane

1607
views
Domanda del libro di testo

Classify each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).

e. norbornane (bicyclo[2.2.1]heptane)

886
views