🏷️ LIMITED TIME OFFER: GET 20% OFF GRADE+ YEARLY SUBSCRIPTION →

HomeClass Notes1,200,000CA670,000

CHM136H1 Lecture Notes - Lecture 36: Lone Pair, Pyrrole, Aromaticity

86 views1 pages

Verified Note

30 Mar 2019

School

Department

Course

Professor

Clive Scott Browning, Kristine Quinlan

For unlimited access to Class Notes, a Class+ subscription is required.

CHM136H1 verified notes

CHM136H1 Lecture Notes - Lecture 35: Benzene, Chlorobenzene, Substitution Reaction

CHM136H1 Lecture Notes - Lecture 36: Lone Pair, Pyrrole, Aromaticity

CHM136H1 Lecture Notes - Lecture 37: Phenyl Group, Phenol, Protonation

Document Summary

While the molecule on the left is not aromatic, if we pull off one of the hydrogens on the lower most carbon, then we form a anion. There will be 6 delocalized electrons just like benzene rings, even though there are only 5 carbons in this ring. The molecule on the right would not satisfy. Huckel"s rule if one of its hydrogens was abstracted and the electrons were left on the carbon. There would be 8 pi electrons and is therefore not aromatic. However, if we form a cation (instead of an anion) by allowing the hydrogen to take both electrons, then, we have 6 pi electrons. Satisfies huckel"s rule and is therefore aromatic. Aromatic ring systems need not be constructed solely from carbon atoms. Heteroaromatics contain elements other than carbon in the ring. In the sample on the right, the lone pair of electrons on the nitrogen atom contribute to the delocalized pi system.

Related Documents

CHM136H1 Lecture Notes - Furan, Aromaticity, Pyrrole

Textbook Guide Chemistry: Heterocyclic Compound, Pyridine, Bromine

CHM136H1 Chapter Notes - Chapter Lab readings: Miscibility, Phenols, Intermolecular Force

blushrhinoceros65

Related Questions

1. Of Huckel's requirements for aromaticity, only this one is NOT required in the case of some compounds to be considered aromatic? 8. Which sequence of reagents would produce b) The system must be monocyclic. c) There must be (4n + 2) Ï electrons. d) The Huckel number of electrons must be completely 2. Zn(Hg), conc. HC delocalized. 2. 4-amino-2-chlorobenzaldehyde is NOz H2N NO2 3. Which of the following compounds are aromatic? Hint: 9. Refer to the following list of possible answers: So ) halogen h) RC-O D diazonium ion a. What group weakly activates benzene to b. What group slightly deactivates benzene to SeAr because a) I and II only c)I, II and â ¢ b) II and III only d) I and IlI only SAr by a +I e-donor inductive effect? of its-I withdrawal inductive effect, but is an ortho-/para- director because of its +R resonance e-donor 4. Which one of the following compounds is anti-aromatie? c. What group inhibits Friedel-Crafts alkylation and acylation d. What species is the electrophile e. What species is formed when but strongly activates a halo benzene to S&Ar because of its strong -R e-withdrawal resonance effect? In which case is the indicated unshared pair of electrons Nora contributor to the Ï aromatic system? 5. in Friedel-Crafts acylation? aniline reacts with NaNO HCVS? 10. Arrange these benzene compounds in order of decreasing (fastest to slowest) SeAr reactivity: . Cyclopentadiene is unusually acidic for a hydrocarbon a) The carbon atoms are all sp hybridized. b) Cyclopentadiene is aromatic. c) Removal of a proton from cyclopentadiene yields an a) III > IV > 11 > 1 c) IV I> III d) IV > â ¡ > I> aromatic anion. d) Removal of a hydride ion from cyclopentadiene What might be predicted to happen when the following substance undergoes Friedel-Crafts acylation? produces an aromatic cation. 11. Recalling that benzene has a resonance energy of 152 k mol and naphthalene has a resonance energy of 255 k mol', predict the two positions which would be occupied by bromine when phenanthrene (below) undergoes addition of Brã (circle two numbers). a) Substitution occurs in ring A, o- to the methylene gro b) Substitution occurs in ring A, o-to the nitro group. c) Substitution occurs in ring A, m- to the methylene g d) Substitution occurs in ring B, o-/p- to the methylene e) Substitution occurs in ring B, m. to the methylene 10 9

1.
Which of the following is true of a cation?
A) it has equal numbers of protons and electrons
B) it has fewer protons than electrons
C) it has more protons than electrons
D) the relationship between protons and electrons depends on thespecific cation
2.
Which is most likely true for an atom with six valenceelectrons?
A) it will gain one electron
B) it will gain two electrons
C) it will lose one electron
D) it will lose two electrons
3.
Which is most likely true for an atom with one valenceelectron?
A) it will gain one electron
B) it will gain two electrons
C) it will lose one electron
D) it will lose two electrons
4.
Which of the following atoms is least likely to form an ion?
A) fluorine
B) magnesium
C) silicon
D) sodium
5.
For which of the following atoms do we not try to apply the octetrule?
A) oxygen
B) nickel
C) sodium
D) xenon
6.
Which of the following is likely to form an ion with the largestpositive charge?
A) potassium
B) calcium
C) aluminum
D) silicon
7.
Which of the following is likely to form an ion with the mostnegative charge?
A) aluminum
B) sulfur
C) chlorine
D) argon
8.
Which of the following ions has the same electronic configurationas neon?
A) Mg2+
B) F -
C) both (a) and (b)
D) neither (a) nor (b)
9.
What is the name of the species formed when a sodium atom loses anelectron?
A) sodate
B) sodide
C) sodium
D) sodium ion
10.
What is the name of the species formed when a bromine atom gains anelectron?
A) bromate
B) bromide
C) bromine
D) bromine ion
11.
Which of the following endings is generally associated with amonatomic anion?
A) ...ade
B) ...ate
C) ...ic
D) ...ide
12.
If the name of an ion ends in "ate" what type of ion is it mostlikely to be?
A) a monatomic anion
B) a monatomic cation
C) a polyatomic anion
D) a polyatomic cation
13.
The preferred name for HSO4- is hydrogen sulfate. What is thecommon name for this ion?
A) bisulfate
B) disulfate
C) bisulfide
D) disulfide
14.
Which pair of species is most likely to form an ionic bond?
A) two electrically neutral species
B) two electrically charged species, one positive and onenegative
C) two negatively charged species
D) two positively charged species
15.
Which of the following situations is most likely to result information of a covalent bond?
A) when an electrically positive species interacts with anelectrically negative species
B) when two nonmetallic elements interact to form a compound
C) when two electrically negative species interact
D) when two electrically positive species interact
16.
Which of the following statements is generally true aboutelectronegativity?
A) electronegativity decreases as we move left to right anddecreases as we move top to bottom
B) electronegativity decreases as we move left to right andincreases as we move top to bottom
C) electronegativity increases as we move left to right anddecreases as we move top to bottom
D) electronegativity increases as we move left to right andincreases as we move top to bottom
17.
For which of the following pairs are the atoms most likely to forman ionic bond with each other?
A) carbon and oxygen
B) calcium and chlorine
C) chlorine and oxygen
D) sodium and magnesium
18.
What is the formula of the compound formed by magnesium andiodine?
A) MgI
B) MgI2
C) MgI3
D) Mg2I
19.
What is the formula of the compound formed between the ammonium ionand the carbonate ion?
A) NH4CO3
B) NH4(CO3)2
C) (NH4)2CO3
D) (NH4)3CO3
20.
What is the formula of the compound formed between the magnesiumion and the acetate ion?
A) MgC2H3O2
B) Mg2C2H3O2
C) Mg(C2H3O2)2
D) Mg(C2H3O2)3
21.
What is the correct name for KI?
A) monopotassium monoiodide
B) potassium iodine
C) potassium iodide
D) potassium ion iodine ion
22.
A compound used to treat manic depressives has the formula Li2CO3.Which of the following is the correct name for this compound?
A) dilithium carbonate
B) lithium carbon trioxide
C) lithium carbonate
D) lithium carboxide
23.
Which of the following bonds is the most polar?
A) H__F
B) H__Cl
C) H__Br
D) H__I
24.
How many electrons are associated with a double bond?
A) 1
B) 2
C) 4
D) 6
25.
How many bonds does a carbon atom typically form?
A) 2
B) 4
C) 6
D) 8
26.
Laughing gas, sometimes called nitrous oxide, has the formula N2O.What is the proper chemical name for nitrous oxide?
A) nitrogen oxide
B) nitrogen dioxide
C) dinitrogen oxide
D) dinitrogen oxygen
27.
Which of the following is the correct formula for dinitrogenpentoxide?
A) O2N5
B) O5N2
C) N2O5
D) N5O2
28.
What is the proper chemical name for water?
A) dihydrogen oxide
B) dihydrogen oxygen
C) hydrogen oxide
D) hydrogen oxygen
29.
To use the VSEPR model to determine the geometry of a molecule weneed to know which of the following?
A) the number of atoms in the molecule
B) the number of atoms bonded to the central atom
C) the number of lone pairs around the central atom
D) both (b) and (c)
30.
What bond angle is most closely associated with a tetrahedraldistribution of electron density?
A) 90o
B) 109.5o
C) 120o
D) 180o
31.
What bond angle is most closely associated with a trigonal planardistribution of electron density?
A) 90o
B) 109.5o
C) 120o
D) 180o
32.
What bond angle is most closely associated with a lineardistribution of electron density?
A) 90o
B) 109.5o
C) 120o
D) 180o
33.
Which of the following molecules is best described as having anearly tetrahedral distribution of electron density?
A) BeCl2
B) OF2
C) SnCl2
D) none of these
34.
In which of the following molecules does the carbon atom have alinear distribution of electron density?
A) C2H2
B) C2H4
C) C2H6
D) none of these
35.
Which of the following is true for the molecule O=C=S?
A) it is nonpolar because it contains only double bonds
B) it is polar because the polarities of the O=C and C=S do notcancel
C) it is polar because it has a bent shape
D) it is nonpolar because it is linear