Question regarding Organic Chemistry

[icevermin]

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My question pertains to a question I found in "ExamKrackers Organic Chemistry" study guide.

This is question 11 found on page 18 if anybody else has the book.

Benzene exhibits resonance. The carbon-carbon bonds of benzene are:
A) Shorter and stronger than the double bond of an alkene.
B) Longer and weaker than the double bond of an alkene.
C) Longer and stronger than the carbon-carbon bond of an alkane
D) Longer and weaker than the carbon-carbon bond of an alkane.

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My answer was A however the book says the correct answer is B. This makes no sense to me and my confusion is furthered by the book's explanation: "The bonds are stabilized by resonance and are shorter and stronger than carbon-carbon alkane bonds but longer and weaker than carbon-carbon alkene bonds"

This is illogical to me as I was taught that benzene, being aromatic, is less reactive than a similar alkene. Thus it must have shorter and stronger bonds?

Thank you.

 

[NickNaylor]

My question pertains to a question I found in "ExamKrackers Organic Chemistry" study guide.

This is question 11 found on page 18 if anybody else has the book.

Benzene exhibits resonance. The carbon-carbon bonds of benzene are:
A) Shorter and stronger than the double bond of an alkene.
B) Longer and weaker than the double bond of an alkene.
C) Longer and stronger than the carbon-carbon bond of an alkane
D) Longer and weaker than the carbon-carbon bond of an alkane.

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My answer was A however the book says the correct answer is B. This makes no sense to me and my confusion is furthered by the book's explanation: "The bonds are stabilized by resonance and are shorter and stronger than carbon-carbon alkane bonds but longer and weaker than carbon-carbon alkene bonds"

This is illogical to me as I was taught that benzene, being aromatic, is less reactive than a similar alkene. Thus it must have shorter and stronger bonds?

Thank you.

Aromatic compounds have completely delocalized electrons, thus there aren't really any double or single bonds. The best way to think about them is 1.5 bonds, if that makes sense. As a result, all of the C-C bonds in benzene are slightly longer than double bonds (and thus weaker than double bonds) and slightly shorter than single bonds (and thus stronger than double bonds).

Benzene compounds are fairly unreactive, but that's because they're strongly resonance-stabilized, not because of their bond lengths.

 

[JP2740]

Yeah it's kind of like, if you draw the resonance forms, Each C-C bond, can either be a double bond or a single bond, so it's somewhere in between.

 

[Excelsius]

Another hint is that you have three answer choices starting with "longer." This is the MCAT, so don't expect to have one absolute answer choice. At least it should make you suspicious.

 

[MaiJMai]

Aromatic compounds have completely delocalized electrons, thus there aren't really any double or single bonds. The best way to think about them is 1.5 bonds, if that makes sense. As a result, all of the C-C bonds in benzene are slightly longer than double bonds (and thus weaker than double bonds) and slightly shorter than single bonds (and thus stronger than double bonds.

I thunk u mean "stronger than single bonds"
?

 

[DSM_302.0]

hey this is great, thanks 🙂

 

[andelJ94]

My question pertains to a question I found in "ExamKrackers Organic Chemistry" study guide.

This is question 11 found on page 18 if anybody else has the book.

Benzene exhibits resonance. The carbon-carbon bonds of benzene are:
A) Shorter and stronger than the double bond of an alkene.
B) Longer and weaker than the double bond of an alkene.
C) Longer and stronger than the carbon-carbon bond of an alkane
D) Longer and weaker than the carbon-carbon bond of an alkane.

---

My answer was A however the book says the correct answer is B. This makes no sense to me and my confusion is furthered by the book's explanation: "The bonds are stabilized by resonance and are shorter and stronger than carbon-carbon alkane bonds but longer and weaker than carbon-carbon alkene bonds"

This is illogical to me as I was taught that benzene, being aromatic, is less reactive than a similar alkene. Thus it must have shorter and stronger bonds?

Thank you.

The dbl bonds in benzene are not true dbl bonds right? the pi electrons can delocalize across the entire ring, so we end up with that toilet bowl figure, meaning the pi electrons are on all C technically. thus, the bonds are longer, weaker than "pure" alkene bonds.