Question

Question 1: Which of the following statement is false about conjugated systems?

Answer 1

Answer:

A conjugated system can only contain two alkenes: False

B. A cumulated diene is less stable than an isolated diene.

False

Explanation:

A. A conjugated system is more stable than an unconjugated system.: True

Due to resonance a conjugated system is more stable.

B. The s-trans isomer is favored over the s-cis isomer.: True

Due to repulsion in s-cis isomer they are less stable.

C. A conjugated system has multiple resonance structures. True

This is the reason they are stable.

D. A conjugated system can only contain two alkenes: False

A conjugated system may have may alternate double and triple bonds.

2) A trans alkene releases less heat upon hydrogenation than a cis alkene.

True

Trans alkenes are more stable than cis alkene. Thus heat of hydrogenation of trans alkene is less than cis alkene.

B. A cumulated diene is less stable than an isolated diene.

False

C. Multiple products can always form when treated a conjugated diene with HBr.  True

There can be 1,2 or 1,4 addition

D. Conjugated systems arise only between sp2-hybridized atoms.

True

Conjugation allows resonance which is possible in sp2 systems

E. Conjugated double bonds involve unhybridized p-orbitals aligned with each other

True

The double bond is formed as pi bond due to side ways overlapping of unhybridized p orbitals