Final Exam Deck Flashcards
(222 cards)
1
Q
Why do atoms bond?
A
Atoms bond to become stable valance electron configuration (8 valence electrons) by bonding with other atoms.
2
Q
What is electronegativity?
A
a measure of the tendency of an atom to attract a bonding pair of electrons
3
Q
What do you mean by dipole moment? Explain, considering water molecule as an example.
A
Dipole moment is a measure of polarity of a molecule bc of the difference of charge on either end of the molecule.
Example> H2O has a permanent dipole moment due to H being much less electronegative than O creating a partial negative charge on the O’s and a partial + on H’s.
4
Q
Why is chloroform (CHCl3) polar whereas carbon tetrachloride (CCl4) is non-polar?
A
CHCl3 has dipole moment with vectors; CCl4 has a not net dipole moment
5
Q
NH3 is a polar molecule but BF3 is non-polar—justify.
A
Because F is evenly distributed around B but H is not evenly distributed around N
6
Q
Describe with suitable diagram(s), the hybridization of carbon in (i) methane
A
Methane (sp3)-
As seen in methane (CH4), carbon can form 4 bonds, bc of hybridization. 1s and 3 p orbitals are being combined to form hybrid orbitals, allowing polyatomic molecule to have 25% s character and 75% p character. Thus, we call methane a sp3-hybridized molecule.
7
Q
Describe with suitable diagram(s), the hybridization of carbon in ethylene
A
Ethylene(sp2)-
Sp2: Unlike methane, ethylene is shaped differently, despite the fact that the carbon in ethylene has the same electron configuration. What accounts for this difference? Supporting evidence shows that the carbon in an ethylene molecule is sp2 hybridized. This means that 1s orbital is being mixed with 2 p orbitals.
8
Q
Describe with suitable diagram(s), the hybridization of carbon in acetylene ( pic
A
Acetylene(sp)-
Sp: Supporting evidence shows that acetylene is an sp molecule. This means that 1s orbital is being mixed with 1 p orbital
9
Q
What do you mean by (i) σ-bond and (ii) π-bond? Explain.
A
sigma bonds are two orbitals overlaping head on and pi bonds are the lobes overlapping
10
Q
Explain the terms “resonance contributor” and “resonance hybrid” considering benzene as an example
A
RC: diff. structures of same molecule each representing a different form that a molecule can take
RH: a dipiction of a molecule showing an intermediate form of all the RC in one
model
Benzene can have 2 different configurations of 3 double bonds and
Benzenes res. hybrid would be drawn with 6 dotted lines representing possible double bonds.
11
Q
What makes resonance structure have decreased stability?
A
-electron delocalization
-increased amount of potential energy/resonance
12
Q
The double bond in cyclohexene can be oxidized by potassium permanganate (KMNO4), whereas the double bonds in
benzene do not undergo this oxidation reaction — Justify.
A
Benzene can not react with KMNO4 because of its resonance structure. Since it has this resonance structure its more stable and therefore does not react.
13
Q
Benzene is aromatic whereas 1,3,5-hexatriene is nonaromatic — Explain.
A
1,3,5-hexatriene is not cyclic
14
Q
Cyclooctatetraene is a cyclic molecule with conjugated π-system having 8 π electrons but it is non-aromatic — Why?
A
is not polar
doesnt follow Huckel’s rule
15
Q
Write the two aspects of the electrophilic aromatic substitution reaction that are affected by a substituent? OR how the rate of the reaction and orientation are affected in EAS?
A
1.Presence of electron donating groups on the benzene makes the second eletrophilic substitution faster and the second substituent come and attack at either para or ortho position
2. Presence of electron withdrawing groups on the benzene makes the second electrophilic substitution less faster and the second substituent come and attack at meta position
16
Q
Define the terms: aromatic, non-aromatic and antiaromatic with examples of cyclopentadienyl cation, cyclopentadienyl anion and cyclopentadienyl radical.
A
the cyclopentadienyl anion is aromatic because it follows Huckel’s rule (4n+2) and it is also because it is planar, and it has two extra electrons which cause aromaticity.
Cyclopentadienyl radical has one extra electron so it does not follow Huckel’s or anti-aromatic rule (4n). The cation version will follow 4n rule; making it anti-aromatic.
17
Q
Write the four requirements of a molecule to be aromatic.
A
1.)Planar structure
2.)Conjugated double bonds
3.) follows (4n+2)
4.) 4 pi electrons
18
Q
Explain Hückel’s Rule of aromaticity.
A
an aromatic compound must have (4n + 2) π electrons, where n = 0, 1, 2, 3….
example: cyclobutadiene meets most of the requirements to be aromatic, but it is NOT because it has 4 π electrons - it is anti aromatic. Benzene, on the other hand, with 6 π electrons, IS aromatic
Explain Hückel’s Rule of aromaticity with examples.
19
Q
Cyclobutadiene is not available to purchase directly from the market — Why?
A
It is unstable and it reacts very fast
20
Q
Clarify the terms: (a) Bonding MO (b) Antibonding MO (c) HOMO (d) LUMO
A
A) where 2 molecules, 2 p-orbitals of similar phase overlap
B) higher energy, becuase it destabilizing node results 2 p-orbitals of opposite phase overlap
C) highest occupied molecular orbital, highest energy orbital not containing electrons
D) lowest occupied molecular orbital, lowest energy orbital not containing electrons.
21
Q
Pyrrole is a heteroaromatic five membered (I) organic base (pKa = 0.4) whereas pyridine is a heteroaromatic six membered (II) organic base (pKa = 5.25). Explain why pyridine is 13 times more basic than pyrrole. (Pic question 20)
A
pyrrole is more acidic because the hydrogen is available, and it is not part of the ring system, and it is more susceptible to reach perride
22
Q
Explain with appropriate figures why o- and/or p- substitution are fovored for EDG whereas m-substitution is preferred for EWG in electrophilic aromatic substitution.
A
The double bond will not make the meta position the most stable because the (+) charge in carbon will go either in ortho and para position
23
Q
Halogens are electron withdrawing but are ortho/para director in electrophilic aromatic substitution-Explain
A
Halogens atoms are highly negative, but have unshared pairs of electrons that can be resonance donated to carbocation
24
Q
What is electrophilic acylium cation? How does it form and affect Friedel-Crafts acylation reaction?
A
resonance stabilized, + charged electrophile; formed by AlCI3 ionizing C-X bond of acid chloride; positive carbon is eletrophilic site to react in EAS
25
Write the mechanism of the Friedel-Crafts acylation of anisole with acetic anhydride.
( pic question 24)
26
Discuss the limitations in electrophilic aromatic substitutions with examples.
-molecule must be aromatic
-acylation can be used only to give ketones.
-F-C reactions dont occur with NH2 groups.
-Benzene ring deactivated by EUG is not electron rich enough do undergo F-C reaction.
27
Go over the examples of the four rules related to additivity of substituent effects in the case of EAS.
Ist rule: if directing effects of 2 subtituents reinforce each other the predicted product predominates
2nd rule: if directing effects of 2 subtituents oppose each other the more activating group dominates
3rd rule: substitutions almost never occur between 2 subtituents meta to each other
4th rule:with a bulky p-director and/or bulky electrohile, para subs predominates
28
Ethyl benzene is treated with (i) Br2 and FeBr3 and (ii) Br2 and light or heat separately. Do you think the products will be same? Justify your answer.
Yes, because the difference # of atoms attracted to it would react differently and attack at different position
29
Go through the oxidation and reduction products of substituted benzenes. Which reagents are used for (i) Clemmensen reduction and (ii) Wolff-Kishner reduction?
i Uses Zn and Hg in presence of strong acid ii.) uses (NH2NH2) and strong base
(КОН)
30
Two hydrogen atoms can combine to form H2 but two He atoms cannot form He2 — Justify from molecular orbital viewpoint.
Two He atoms came from He2 whereas two
H atoms on H2 form because number of electrons of HOMO must be more than number of electrons in LUMO.
31
What is ipso substitution? Give an example [structures need to be drawn].
Describes two substituents sharing the same ring position in an intermediate compound in an electrophilic aromatic substitution.
32
Why aromatic compounds are more stable than their aliphatic counterpart? Draw the MO diagram of benzene.
because they have lower energy, more stability.
33
What is the relation between numbers of node with energy of the orbital?
More the nodes that are the more the energy it has and the less stable it becomes
34
Cycloheptatrienylium cation is more stable than Cycloheptatriene — Why?
Planar, follows Heckel’s rules making it more stable, not planar and not aromatic
35
Cyclopropenyl cation is a planar molecule. Is it “Aromatic”, “Non-aromatic” or “Antiaromatic”?
Aromatic
36
Imidazole with 8 π electrons is aromatic — Why?
Because it only uses one lone pair in the conjunction Pi system
37
Furan with 8 π electrons is aromatic — Why?
Because one of the lone pair of electrons of the oxygen atom is delocalized in the ring
38
Thiophene with 8 π electrons is aromatic — Why?
Because one of the lone pair of electrons of the sulfur atom is delocalized in the ring
39
Pyrene with 16 π electrons is aromatic — Justify.
Becuase the Pi bond in the middle of the ring is not participating in resonance
40
The compound [10] Annulene is not aromatic — Justify.
Hydrogens interfere preventing polarity
41
What do you mean by “Pericondensed” and “Catacondensed” polycyclic aromatic hydrocarbons (PAHs)? Give two examples in each case (structures are required).
Pericondensed: more than one internal
carbon node,
Pyrene and coronene
Catacondensed: No internal carbon
vertices
Naphthalene and phenanthrene
42
EAS can be considered as Lewis acid-Lewis base reaction — Justify.
Because it receives an electrophile attacking a carbon atom
43
The boiling points of o-, m-, and p-Xylenes are 144 °C, 139 °C and 138 °C respectively — Justify.
boiling point dependent upon dipole moment; ortho>meta›para for disubstituted benzenes
44
How the electrophilicity of bromine (a weak electrophile) can be increased by using FeBr3
Br is weak electrophile; when FeBr3 used,
Br electrophilicity increased bc creates polarized bromine; polarized bromine serves as Br+ for electrophile to be added & form carbocation
45
Write the name of the electrophiles in nitration and sulfonation reactions?
Nitration- Nitronium ion (+NO2)
Sulfonation- Sulfonic ion (+SO3H)
46
Write the difference between ‘reagent’ and ‘catalyst’ of a reaction.
Catalyst accelerates the rate of the reaction but it doesn’t get by the reaction, and the reagent initiates the reaction and it gets consumed
47
Write the name and resonance structures of the electrophile in Friedel-Crafts acylation reaction.
Acylium ion
48
Why n-Propylbenzene cannot be synthesized by Friedel-Crafts alkylation reaction?
because alkylation will give a product of isopropylbenzene it will be acylation that will yield propylbenzene by reduction
49
The abbreviation NAS stands for
Nucleophilic Aromatic Substitution
50
Meisenheimer Complex is formed addition-_______________ mechanism of ______ reaction.
elimination, NAS
51
Benzyne is formed in …………. aromatic substitution reaction.
nucleophilic
52
The state of hybridization of the triple bonded carbons in benzyne is…………….
sp2
53
Phenylation to 1,3-diketo compounds is an example of ……………………reaction.
NAS
54
Give an example with figure (in each case) of terminal alkene, internal alkene, and cycloalkene.
55
In ethylene, the carbons are…………..hybridized.
sp2
56
Bromination of cis-2-butene produces a racemic mixture whereas trans-2-butene produces a meso compound-why?
Because halogen additions are determined by anti-addition and completely restricted rotation of the carbon-carbon bond of the halonium ion
57
Write the stability order of 1-butene, cis-2-butene, and trans-2-butene
1-butene < cis-2-butene < trans-2-butene
58
What is Markovnikov’s rule?
Mark’s rule states that in the addition of (hydrogen halides) to an unsymmetrical alkene, the H atom adds to the more substituted carbon atom— that is the carbon that has the greater number of H atoms to begin with.
59
What is Anti-Markovnikov’s condition? Give an example
-a mechanism that avoids the carbocation intermediate
-the halogen adds to the less substituted carbon.
Ex: addition of hydrogen bromide to propene in the presence of benzoyl peroxide.
59
In the case of hydrohalogenation reaction………………..…..and ………………….….addition occur.
syn; anti
60
What do you mean by vicinal and germinal dihalides? Give example in both cases.
Vicinal: halides are next to each other
Geminal: relationship between 2 atoms or functional groups attached to same atom
61
Vicinal dihalide
when halogens are on adjacent carbons
62
Germinal dihalide
when both halogens are on the same carbon
63
What do you mean by halohydrin? How does it form?
A halohydrin is an organic molecule that contains both a halogen and an OH group.
Halo=halogen and Hydrin=OH.
AKA when a halogen and a hydroxyl are bonded to adjacent carbon atoms
64
How does a halohydrin form?
-Reaction Overview: the halohydrin formation reaction involves breaking a pi bond and creating a halohydrin in its place.
-by treatment of an alkene with a halogen X2 and H2O forms the halohydrin by addition of the elements X and OH to the double bond
65
What is NBS?
N-bromo succinimide is a useful reagent in organic chemistry
66
What purpose does NBS serve in organic synthesis?
(N-bromosuccinimide)
In H2O, NBS decomposes to form Br2, which then goes on to form a bromohydrin in aqueous DMSO by the same reaction mechanism as halohydrin formation
-In other words, Wohl-Ziegler reaction.
67
Hydroboration-Oxidation is an anti………………addition to alkenes.
Markovnikov
68
What is 9-BBN? Mention its use in organic synthesis.
9-boracicyclo[3.3.1] none or
9-BBN is a hydride-bridged primer, which cleaves in the presence of reducible substrates.
-This colorless solid is used in organic chemistry as a hydroboration reagent.
69
Mercurinium ion is formed in………………reaction.
oxymercuration
70
Oxymercuration-Demercuration is a ……………….hydration procedure.
indirect
71
What is the degree of unsaturation?
Degree of unsaturation is the number of pi bonds and/or rings in the molecule
72
Explain the degree of unsaturation considering C6H10 as an example.
-C6H10 has a degree of unsaturation of 2
-this means that C6H10 may contain 2 rings, 2 pi bonds, 1 ring and pi bond, or 1 triple bond
73
Hydrogenation is a ……………addition.
syn
74
Peroxyacetic acid is used in ………………reaction of alkenes.
epoxidation
75
When 2 substituents are added on the same side/face of a double bond
syn
76
When 2 substituents are added on opposite sides/faces of double bond
anti
77
Explain the terms syn and anti with appropriate examples.
Syn addition is the addition of two substituents to the same side of a double/triple bond, resulting in a decrease in bond order but an increase in number of substituents.
Generally the substrate will be an alkene or alkyne.
Anti addition: an addition reaction in which two substituents are added to opposite sides of a double bond.
78
…………..is an aliphatic peroxyacid whereas ………………is an aromatic peroxy acid.
peroxyacetic acid; m-chloroperbenzoic acid
79
The product of the reaction between an alkene with HBr is………….whereas the product between the
reaction of an alkyne with HBr is…………..
an alkyl bromide; a vinyl bromide
80
What is keto-enol tautomerism? Give an example from nature.
Tautomers are isomers that can convert via migration of a proton, accompanied by a switch of a single bond and an adjacent double bond.
Ex: turmeric, as it contains curcumin as an active ingredient
81
What is Lindlar catalyst?
catalyst made from palladium on calcium carbonate that performs the hydrogenation of alkynes in the presence of H2
82
The hydrogenation of an alkyne with Lindlar catalyst produces…………..alkene whereas the treatment with Li/NH3 produces…………
cis alkene; trans alkene
83
Carbon dioxide is produced as a byproduct during oxidative cleavage of …………..alkynes.
terminal
84
Write the name of four strong oxidizing reagents.
O3-ozone
KMNO4-potassium permanganate
H2O2-hydrogen peroxide
HNO2-nitrous acid
85
Acetylide anion is formed on the treatment of…………………..with acetylene.
a strong anhydrous base
86
Isomeric compounds that rapidly interconvert by the movement of a ………………. are called………..
proton; tautomers
87
Treatment of an alkene with a halogen X2 and H2O forms …………………….
halohydrin
88
Nucleophilic aromatic substitution can occur when……………… groups are ortho or para to the halogen
atom.
strong electron withdrawing group
89
Nature produces ……….. alkene exclusively and Oils are derived from ……… having a larger number of
double bonds.
cis; fatty acids
90
The addition of HBr to an alkene generates ………………carbocation whereas …………..carbocation is
generated during the addition of HBr to an alkyne.
an alkyl secondary carbocation; a vinylic secondary carbocation
91
Which of the following compounds is least reactive towards NAS?
1-bromo-3-nitrobenzene
92
Formula for degree of unsaturation?
(2n+2) - x / 2
93
C44H64O2
Crocin
94
Translate this to form where degree of unsaturation can be calculated:
C6H5N
C6H4
95
Translate this to a form where degree of unsaturation can be calculated:
C6H5NO2
C8H12
96
Translate this to a form where degree of unsaturation can be calculated:
C9H16Br2
C9H18
97
Translate this to a form where degree of unsaturation can be calculated:
C10H12N2O3
C10H10
98
Translate this to a form where degree of unsaturation can be calculated:
C20H32ClN
C20H32
99
Translate this to a form where degree of unsaturation can be calculated:
C44H64O2+
C44H64
100
What are the basic differences between SNAr reaction with SN1 and SN2 reactions?
SN1/SN2 = alkyl halides
SNAr = dissociation & stable carbocation
SN2 = Nu back attacks as LG leaves
SNAr = flat ring so no back attack & no dissociation
addition-elimination = meisenheimer
elimination-addition = benzyne intermediate
101
Use chlorobenzene as an example for why SNAr reactions are not considered either SN1 or SN2
-chloronbenzene and SN1 not happen bc a positive charge is created on the ring;
-chlorobenzene is not an SN2 reaction bc steric hindrance is created.
SNAr will bc if strong EWG at ortho/para through addition elimination = Meisenheimer complex
102
What is benzyne?
intermediate formed in elimination-addition reaction; when there is no EWG
103
Why 2-chloropropane is formed as the sole product in the reaction between propene and HCl? Explain with mechanism.
propene is unsymmetrical to MKV rule = H-less substituent
104
Why secondary carbocation is more stable than primary carbocation? Explain the details.
Secondary carbocation has lower activation energy so a faster reaction & lower effect
105
Discuss the mechanism (drawing is essential) of the electrophilic addition of water to 1-methylcyclohexene.
hydration-electrophilic addition of water; pi bond attacks H3O+; electrophile added to pi bond; formed carbocation; Nu (H2O) attacks carbocation; water removes proton & forms alcohol; acid catalyzed
106
How TMBE can be synthesized from the electrophilic addition of alcohol to alkenes?
tert-butyl methyl ether; ELECTROPHILIC ADDITION; methanol and 2-dimethylpropene; catalyzed by H2SO4; MKV rule
107
Draw and explain the mechanism of bromination of cis-2-butene
halogenation; electrophile added to pi bond; breaks/forms 4 bonds = rate determining.; bridges bromonium ion; nucleophilic attacks ion; racemic mixture with cis bc added anti
108
Why is hydroboration regioselective? Explain the mechanism considering hydroboration-oxidtion reaction to propene.
steric factor & electronic/inductive effects; BH3 added to alkene, large group to less hindered & adjacent methyl stabilizes partial positive charge
109
Explain the stepwise mechanism of the reaction between mercury (II) acetate to ethylene.
mercury (II) acetate dissociates = +Hg(OAc); attacks pi bond and forms mercurinium ion; water approaches ion from anti to ring; MKV = water added to more substituted
110
What is ozonolysis? Explain with stepwise mechanism.
oxidative cleavage of alkene to carbonyl; pi and sigma bonds broken & replaced with C=O bonds; ozone has both nucleophilic and electrophilic capabilities
111
Explain with suitable examples the concept of E- and Z- alkenes. Is there any difference between cis/trans with E/Z? Justify your answer.
when 3 or 4 different groups use E/Z instead of cis/trans; visually split double bond and asses priority of each side
E = higher priority on opposite sides
Z = higher priority on same side
112
Cis-2-butene has a higher boiling point (40C) than trans-2-butene (10C) - explain
2 methyls on same side of cis form net dipole moment; polar = higher bp
113
How can you correlate the melting points of oleic acid, linoleic acid, and linolenic acids with their double bonds?
fatty acid w same number of C that increases in double bonds = mp decreases
114
What is mercurinium ion? When does it form?
it is a cyclic intermediate with + charge; results from + Hg(OAc) reacting with alkene; oxymercuration rxn
115
Hydration of terminal alkynes in the presence of mercuric sulfate always yields a methyl ketone whereas hydration of internal alkynes produces mixture of ketones. Explain with appropriate example.
terminal = methyl ketone bc addition of water is MKV
115
What is keto-enol tautomerism? Explain with the example of curcumin.
enols rearrange to form ketones through movement of proton from OH to alkene carbon; ketone more stable
116
Hydroboration-oxidation of an internal alkyne produces ketone whereas the same reaction for a terminal alkyne yields aldehyde-why? State the rule associated with this.
anti-MKV bc of the way H2O is added
117
Oxidation (KMnO4 or ozone) of unsymmetrical internal alkynes produces two carboxylic acids whereas under the same condition terminal alkyne produces one carboxylic acid. Explain
terminal alkynes oxidize and form carboxylic acid and CO2
118
Write the (i) reagents and (ii) mechanistic steps and (iii) explanation associated with the following reaction:
i.) 6-C alkyne, NaNH2, NH3, alkyl halide
ii.) produce hydrocarbon that leads to larger alkynes; acetylide anion reacts with alkyl halide; transition state until halide leaves; inversion of configuration since SN2
119
What is the hybridization state of the carbon attached to the alcoholic OH group?
SP3
120
What is the hybridization state of the oxygen in the alcoholic OH group?
SP3
121
2-pentanol is a … alcohol.
secondary
122
The IUPAC name of allyl alcohol is……………
3-propenol
123
The IUPAC name of n-amyl alcohol is…………….
1-pentanol
124
Alcohols form ………………. ion in the presence of a strong acid.
oxonium ions
125
The order of reactivity of alcohols with alkali metals is………………….
primary > secondary> tertiary
126
The oxidation state of carbon in methanol………………………………
-2 (-4 +2 = -2)
127
K2Cr2O7/H2SO4 is used for ………………………. reaction.
oxidation
128
Primary alcohols oxidize to form …………., which then oxidize to form …………………….
aldehydes; carboxylic
129
Secondary alcohols oxidize to form …………………….
ketones
130
Pyridinium chlorochromate (PCC) is used for …………………of alcohols to the corresponding……….
oxidation; aldehyde
131
A protonated alcohol is called ………………………
oxonium ion
132
Na2Cr2O7/acetic acid is used for ………………………. reaction.
oxidation (secondary alcohols)
133
Ethyl alcohol on chromic acid oxidation produces………………………
green color due to chromium (III) oxide formation / aldehyde
134
In the “alcohol breath analyzer test,” the chemical used is……………
ethanol or
potassium dichromate
135
Ethanol is oxidized in the liver to produce…………………
ethanal
136
The common name of picric acid is…………………….
trinitrophenol (TNP) or 2,4,6 - trinitrophenol
137
The active irritants in poison ivy and poison oak are………………….
urushiols
138
The phenolic compound which is used as an acid-base indicator is…………………………….
phenaphthalein
139
The toxicity of phenols to micro-organisms makes them excellent ………….
antiseptics
140
The compound 4-hexylresorcinol is used as an……………………….
antiseptic
141
Alcohols and phenols are weak……………………acids.
bronsted
142
Methanol is more acidic than ethanol—why?
-alkyl groups make an alcohol a weaker acid
-since ethanol has a longer alkyl chain than methanol, ethanol is a weaker acid
-methanol is therefore more acidic
143
Electron-withdrawing groups (EWGs) make an alcohol a stronger …………… by stabilizing the ……………………. base.
acid; conjugate base
144
Alcohols are weak acids and require a strong base to form the corresponding …………….
alkoxides
145
An electron-withdrawing substituent makes a phenol more …… by ………………. the negative charge.
acidic; delocalizing
146
Reduction of ……………………. gives primary alcohols, whereas reduction of ketones gives ………………… alcohols.
aldehydes; secondary
147
Lithium aluminum hydride (LiAlH4) is a more powerful reducing agent than ……………………. but less specific, and very
reactive with ……………
sodium borohydride (NaBH4); water
148
Which reducing agent would you prefer to reduce carboxylic acids to primary alcohol?
LiAH4 (lithium aluminum hydride)
149
Treatment of secondary and tertiary alcohols with phosphorus oxychloride in pyridine at low temperature
follows………………. route.
EZ elimination reaction
150
If 1° and 2° alcohols are treated with SOCl2 or PBr3 the reaction follows ……………….mechanism.
SN2
151
Alkyl tosylates react like alkyl …………
halides
152
The SN2 reaction of an alcohol via an alkyl ……………… proceeds with ………. inversion.
halide; secondary
153
Grignard reagents react with …………… compounds to yield………………
carbonyl; alcohols
154
An ether solvent is essential for the formation of a …………….
Grignard reagent
155
The non-bonded electrons from an ether help to …………..a Grignard reagent.
stabilize
156
The first part of the Grignard reaction is the formation of the Grignard reagent. This mechanism involves
a…………………reaction.
radical-transfer
157
Grignard reagents act as……………….. in adding to a carbonyl group.
nucleophilic carbon anions (carbanions)
158
Thiols are organic compounds that contain the ……….. group, also called……………….
-sulfhydryl group; mercaptans
159
Tetrahydrofuran (THF) is a solvent that is a ……………… ether.
cyclic
160
The IUPAC nomenclature of diethyl ether is…………………………
ethoxy ethane
161
The other name of epoxy-alkane is ………………………….
epoxide
162
An anticancer drug with oxirane moiety is ………………….
epothilone B
163
Ethers oxidize in air to form explosive ……………………. and ……………………….
hydroperoxides and peroxides
164
“Crown” ethers are useful as …………………. in nucleophilic substitution and other reactions
enhancers
165
The Williamson Ether Synthesis follows ……………………….route.
SN2
166
The anti-hypertensive B-Blocker drug (Propranolol) can be synthesized by exploring……………ring-opening methodology.
base-catalyzed epoxide
167
A naturally occurring polyether that interferes with Na+ ion transport across cell membranes is ………………………….
brevetoxin (neurotoxin)
168
The ………………. ring opening methodology is used to synthesize the bronchodilators salmeterol and albuterol.
unsymmetrical (attack w/nitrogen nucleophile)
169
What do you mean by host-guest complex? Indicate the ‘host’ and the ‘guest’.
-host-guest complex –> a crown ether-cation complex
-the crown ether is the ‘host’
-the cation is the ‘guest’
170
What is molecular recognition?
the ability of a host molecule (crown ether) to bind to specific guests (cations)
171
The ability of crown ethers to complex cations can be exploited in …………….
Nucleophilic substitution reactions
172
Oxirane is a synonym of
(i) oxygen
(ii) metal oxide
(iii) anhydrous alcohol
(iv) epoxide
(v) octane.
(iv) epoxide
173
How to name crown ethers:
of atoms - crown - # of oxgens
174
Intramolecular Williamson’s ether synthesis is an example of………………….reaction. ( e.g. SN1, SN2, E1, E2 etc.).
SN2
175
Nitrogen atom with a lone pair of electrons, making amines both ……………. and…………………….
basic and nucleophilic
176
Know the common names of heterocyclic amines as provided in the PPT.
-pyridine
-pyrrole
-quindine
-indole
-pyrimidine
-pyrrolidine
-piperidine
177
Amines with fewer than ……………………………. carbons are water-soluble.
5
178
Primary and secondary amines form …………………… bonds, increasing their boiling points
hydrogen
179
The nitrogen of an amine can behave as a……………………
nucleophile
180
Amines are stronger ……………………… than alcohols, ethers, or water.
bases
181
A phthalimide alkylation for preparing a primary amine from an alkyl halide is known as ………………………. synthesis.
Gabriel
182
Carboxylic acid derivatives can be converted into primary amines with loss of one carbon atom by both the
……………………. rearrangement and the ………………………… rearrangement.
Hofmann and Curtis
183
Alkyl azides are not nucleophilic, but they are ……………………
explosive
184
Why are arylamides instead of arylamines used for Friedel-Crafts Reactions of arylamines?
the amino group in arylamines forms a lewis acid-base complex with the AlCl3 catalyst, preventing further reaction. Therefore, the corresponding amide must be used
185
Azo-coupled products have extended conjugation that leads to low energy ……………. transitions that occur in visible
light (dyes).
electron
186
In amines, the nitrogen is ………………. hybridized.
SP3
187
In amides, the C=O group is strongly electron-withdrawing, making the nitrogen very
(a) weak base
(b) strong base
(c) weak acid
(d) strong acid (e) electron-rich
(a) weak base
188
Example of electron donating and electron withdarwing groups are:
(a) ⎯CH3, ⎯NH2
(b) ⎯OCH3 and ⎯CH3
(c) ⎯Cl,⎯NO2
(d) ⎯CN, ⎯CH3
(e) ⎯CH3, ⎯CN
e) -CH3, -CN
189
The product of Hofmann elimination is
(a) alkane
(b)alkyl halide
(c) acyl azide
(d) alkene
(e) isocyanate
(d) alkene
190
Primary arylamines react with nitrous acid (HNO2), yielding stable …………….. salts. This reaction is known as
…………………………reaction.
the sandmeyer
191
Base-promoted hydrolysis of an ester is called……………………………
saponification
192
Fischer esterification
Treatment of a carboxylic acid with an alcohol in the presence of an acid catalyst is known as………….
193
Nucleophilic acyl substitution is the characteristic reaction of …………………… derivatives.
carboxylic acid
194
Tetrahedral intermediate is formed in…………………….
Nucleophilic acyl substitution reactions
194
The carbon atom on the C(triple bond)N group is …. hybridized, making it linear with a bond angle of ……
SP; 180
195
Nucleophilic …….. substitution is the characteristic reaction of ………… derivatives.
acyl; carboxylic acid
196
The carbon atom on the C(triplebond)N group is SP hybridized, making it linear with a bond angle of ________
180
197
Why are two equivalents of ammonia required to prepare a primary amide from a carboxylic acid chloride?
One equivalent acts as the nucleophile to replace Cl, while the other reacts as a base with the HCl (byproduct)to form a quaternary ammonium salt. If the acid is not neutralized, the reaction becomes reversable.
198
Nucleophiles that are also strong …….. react with carboxylic acids by removing a ……. first, before any nucleophilic
substitution reaction can occur.
bases; proton
199
Treatment of a carboxylic acid with ………………….. affords an acid chloride.
thionyl chloride (SOCl2)
200
……………. of a carboxylic acid occurs in the presence of acid but not in the presence of a base.
Esterification
201
Intramolecular esterification is known as ……………whereas intramolecular amidation is known as ………..
lactamasation; lactomasation
202
Dicyclohexylcarbodimide (DCC) is a …………….. .agent.
dehydrating
203
Nitriles are prepared by ……………. reactions of unhindered methyl and 1° alkyl halides with ¯CN.
SN2
204
…………….. are the ………….most reactive of the carboxylic acid derivatives.
?
205
The tautomeric form of amide is known as ………acid.
imidic
206
Know the rule to predict the major/minor products in the elimination reaction of alcohols.
“Saytzeff’s rule”.
207
Write a note on “Saytzeff’s rule”.
during intramolecular dehydration, if there is a choice of positions for the Carbon carbon double bond, the preferred location is the one that generally gives the more highly substituted alkene - that is, the alkene with the most alkyl groups attached to the double bonded carbons
208
The boiling point of ethanethiol (36 °C) is less than half of that of ethanol (78 °C) — Why?
Thiols boil at lower temperatures than alcohols because hydrogen bonds cant form between thiol molecules but can form between alcohol molecules. The more hydrogen bonds, the higher the boiling point
209
Arylamines and heterocyclic aromatic amines are considerably less basic than alkylamines — Justify. (3)
-The N lone pair electron in arlyamines is delocalized by interaction with the aromatic ring pi electron system
-it is therefore less able to accept H+ than alkylamines
-arylamines and heteroaromatic (heterocyclic aromatic) amines are considerably less basic than alkyamines (conjugate acid pKa = 5 or less)
210
Tertiary amines cannot form intermolecular H-bonds——Justify. (3)
-the structure of tertiary amines are R3-N
-all bonds made with Nitrogen are alkyl groups, so there are no hydrogens bonded to the nitrogen.
-With no hydrogens, H-bonding cannot occur.
211
Write a note on Curtius rearrangement.
carboxylic acid derivatives can be converted into primary amines w/ loss of one carbon atom by both the Hofmann rearrangement and the Curtius rearrangement
212
Arylamines are not useful for Friedel-Crafts reactions”—Why?
the amino group forms a lewis acid-base complex w/ the AlCl catalyst, preventing further reaction
213
Which unique characteristic of alcohol helps to increase its boiling temperature?
Alcohols form hydrogen bonds. A positively polarized -OH hydrogen atom from one molecule is attracted to a lone pair of electron on a negatively polarized oxygen atom of another molecule. The intermolecular attractions are present in solution but not in the gas phase, thus elevating the BP of the solution.
214
Explain why 4-nitrophenol is more acidic than 4-aminophenol with suitable resonance contributors.
-In 4‑nitrophenol, the nitro group withdraws electron density from the ring via strong –I and –R effects, stabilizing the negative charge on the oxygen in the phenoxide ion.
-In 4‑aminophenol, the amino group donates electron density (via +R effect) into the ring, destabilizing the negative charge on the oxygen.
Thus, the greater stabilization of the anion by the electron-withdrawing nitro group explains why 4‑nitrophenol is more acidic than 4‑aminophenol.
215
The boiling point of ethanethiol (36 °C) is less than half of that of ethanol (78 °C) — Why?
Thiols boil at lower temperatures than alcohols because hydrogen bonds cant form between thiol molecules but can form between alcohol molecules. The more hydrogen bonds, the higher the boiling point.
216
What is “Williamson Ether Synthesis”? Write down the limitation(s) of this synthesis.
SN2 reaction of a prmary alkyl halide (substrate) and an alkoxide (nucleophile) to yield ethers.
-Limitations: Alkyl halide must be primary and the alkoxide ion can be derived from primary, secondary or tertiary alcohols.
217
Amides are less basic than the corresponding amines — Justify.
In the amines, the nitrogen have a lone pair of electrons that can be given up. In an amide, the lone pair of the nitrogen is close to an oxygen, and as a result gets involved with resonance and is no longer able to be given up.
218
What is “Claisen rearrangement”?
In the Claisen rearrangement of an allyl vinyl ether undergo a sigma tropic rearrangement which form a carbonyl and an alkene group on heating.
219
Arylamines and heterocyclic aromatic amines are considerably less basic than alkylamines — Justify.
The N lone pair electron in arlyamines is delocalized by interaction with the aromatic ring pi electron system - it is therefore less able to accept H+ than alkylamines -arylamines and heteroaromatic (heterocyclic aromatic) amines are considerably less basic than alkyamines (conjugate acid pKa = 5 or less)
