Quiz 6-9 + Worksheets Flashcards
The larger the number of Pkb, the ______ the _____ (base/acid).
Weaker; base
Is CH3 a deactivator/activator?
Activator
Electron withdrawing groups are mostly ___________ (deactivators/activators).
deactivators
List some deactivators.
CN (triple bond)
NO2
SO3H
C=OH … carbonyls
N+R3
Halogens
How to find Pkb from Pka?
Subtract Pka value from 14.
Is 1,3,5-trihexene aromatic, non aromatic or anti aromatic? Why?
Non aromatic because it is not cyclic.
A deactivator as a substituent on a benzene reacting with Br2, FeBr3 produces what major product?
An addition of Br on the meta position of the substituent.
What kind of director is NH2?
Ortho/para-director.
Why is sulfuric acid used in aromatic nitration?
Because of the tert-butyl cation.
What kind of director is OCH3?
Para/ortho-director…activator
What kind of director is OH?
Para/ortho director…activator.
What kind of director are amines?
Para/ortho-director…activator.
Is -NHC=OCH3 a meta directing group?
No, because it is part of the amine group.
Which has a UV absorption band at the longest wavelength between a conjugated cyclic and conjugated non-cyclic compound?
Cyclic compound.
Can isolated alkenes undergo Diels-Alder reactions?
No.
A diene with a OCH3 substituent on the 2nd position and a dienophile with a CHO substituent produces what kind of product?
A 1,4-product.
The carbon-carbon bonds in benzene are…
of equal length and intermediate between a double bond and a single bond.
How many pi-bonding MOs are in benzene?
3
What is the difference between the modern Kekule structures and the original Kekule structures?
The C-C bond lengths in the modern structures are all the same and the modern structures are two resonance structures.
Which reaction do benzene tends to undergo?
Substitution rather than addition reactions.
What are non-bonding orbitals?
The HOMO and the LUMO MOs.
What are the non-bonding MOs of cyclobutadiene?
p2 and p3.
Which of the following concepts are used to describe the structure of benzene?
Unsaturation
Harmonic aromatization
Saturation
Resonance
Resonance
Another name for cyclobutadiene is…
[4]annulene
Is a not basic N (in a cyclic compound) strong or weak base?
Weak base.
NH is _____ while N is ______.
not basic; basic
Does conjugation increases acidity?
Yes.
An ethene substituent added to a benzene is called…
Styrene
Describe napthalene’s structure.
2 benzenes together.
A cyclopentane substituent attached to a benzene is called…
Cyclopentylbenzene
or
phenylcyclopentane
What is the electrophile in the bromination of benzene?
Br+
A carbocation at a tertiary carbon is _______ (stable/not stable).
Not stable.
When toulene reacts with Br2, why does it not go through addition to form a vicinal dihalide?
It is highly unfavorable because it would result in a nonaromatic product.
Name one major difference between the aromatic and antiaromatic compounds.
Only aromatic compounds follow Huckle’s Rule.
Based on Hammond’s Postulate, if the carbocation intermediate is antiaromatic, what can you expect from the reaction?
The activation energy needed to produce the intermediate would be very high.
Why is pyrrole a much weaker base than pyridine?
When pyrrole is protonated, the system’s aromaticity is destroyed.
Name C3N2H4.
Imidazole.
Describe or draw imidazole compound.
C3N2H4 (two double bonds)
As conjugation ___________, the HOMO-LUMO energy gap becomes _________, and the wavelength of light absorbed becomes __________.
increases; smaller/narrow; longer
What does degenerate mean?
“Have the same energy”.
How many degenerate bonding MOs does benzene have?
2 (pi 2 and pi 3)
Antiaromatic compounds are ________, fully _____________, making them highly _________, similar to a ________ (cation/anion/radical).
unstable; conjugated; reactive; radical
Deactivator __________ (decreases/increases) the rate of reactivity toward electrophilic aromatic substitution.
decreases
Rank in order of stability. Least to greatest.
Cumulative
Conjugated
Isolated
Cummulated < Isolated < Conjugated
