Chapter 10 Flashcards
1
Q
Alcohol
A
A hydroxyl group bonded to an sp^3 hybridized carbon
2
Q
How are alcohols classified?
A
As primary secondary or tertiary, depending on whether the hydroxyl group is bonded to a primary, secondary, or tertiary carbon.
3
Q
How are IUPAC names of alcohols derived?
A
By changing the suffix of the parent chain from -e to -ol
4
Q
How are the carbon chains of alcohols numbered?
A
From the direction that gives the carbon bearing the hydroxyl group the lower number.
5
Q
How are compounds containing other functional groups that take higher precedence named?
A
The presence of the hydroxyl group is indicated by the prefix hydroxy-
6
Q
How is the oxygen atom of an alcohol hybridized?
A
sp^3 (remember the unshared electron pairs)
7
Q
___ sp^3 hybrid orbitals of oxygen form __ bonds to atoms of carbon and hydrogen, and the remaining ___ sp^3 hybrid orbitals each contain an unshared pair of electrons
A
Two, sigma, two
8
Q
What is the parent alkane for an alcohol?
A
The longest chain of carbon atoms containing the -OH group.
9
Q
To show the compound is an alcohol:
A
change the suffix-e to -ol and use a number to show the location of the -OH group
10
Q
The location of the -OH group takes precedence over __________ in numbering the parent chain.
A
alkyl groups and halogen atoms
11
Q
For cyclic alcohols, numbering begins with the carbon:
A
containing the -OH group
12
Q
Should the number location of the -OH group be stated in cyclic alcohols?
A
No
13
Q
In complex alcohols, the number for the hydroxyl group is often:
A
placed between the infix and the suffix
14
Q
Diol
A
A compound containing two hydroxyl groups
15
Q
Triol
A
A compound containing three hydroxyl groups
16
Q
In IUPAC names for diols, triols, and so on, the ___ of the parent alkane name is retained.
A
final -e
17
Q
Glycols
A
Compounds containing hydroxyl groups on adjacent carbons
18
Q
Unsaturated alcohols
A
Compounds containing -OH and C=C groups
19
Q
Alcohols are ______ compounds with oxygen bearing a partial _______ charge and both the carbon and the hydroxyl hydrogen bearing partial ______ charges.
A
polar, negative, positive
20
Q
Hydrogen bonds
A
Relatively strong attractive interactions between a hydrogen atom bonded to an atom of high electronegativity, usually O or N, and a lone pair of electrons on a highly electronegative element, again, usually O or N.
21
Q
The boiling points of alcohols are _____ than those of hydrocarbons of comparable molecular weight. Why?
A
higher
Because of the intermolecular association of hydrogen bonding
22
Q
The boiling points of alcohols ______ with increasing molecular weight. Why?
A
increase
Because of increased dispersion forces
23
Q
Alcohols are ____ soluble in water than hydrocarbons of comparable molecular weight. Why?
A
more
Alcohols interact with water by hydrogen bonding
24
Q
What intermolecular forces do alcohols contain?
A
LDF, dipole-dipole, and hydrogen bonding
25
Hydrogen bonding is ______ than covalent bonding.
weaker
26
Alcohols can function as both ____ acids (proton _____) and _____ bases. (proton ______)
weak, donors, weak, acceptors
27
The pKa of most alcohols is:
in the range of 16-18
28
Loss of a proton from an alcohol produces:
An alkoxide anion, a relatively strong base
29
In the presence of a strong acid, the -OH group can be _______.
protonated
30
Protonation of the -OH group produces:
The good leaving group -OH2+ (a common mechanistic scheme for alcohols)
31
In dilute aqueous solution, methanol and ethanol are comparable in acidity to _____.
water
32
Secondary and tertiary alcohols are somewhat ______ acids than primary alcohols and water.
weaker
33
In dilute aqueous solution, only ______ is more acidic than water.
methanol
34
_______ molecular weight, _______ alcohols are slightly weaker acids than water.
higher, water-soluble
35
For simple alcohols such as methanol and ethanol, acidity depends on:
the degree of solvation and stabilization of the alkoxide ion by water molecules
36
In the presence of strong acids that generate hydronium, the oxygen atom of an alcohol is a(n) _____ and reacts with a(n) ____ by proton transfer to form a(n) _______.
base, acid, oxonium ion
37
Alcohols react with active metals such as ________ to:
Li, Na, K
liberate H2 and form metal alkoxides
38
Metal alkoxides are nearly ____ or somewhat _____ bases than alkali metal hydroxides, such as NaOH and KOH
the same, stronger
39
What kind of reaction is the reaction of alcohols with active metals?
An oxidation/reduction reaction
40
In the reaction of alcohols with active metals, the active metal (Met) is _______ to ____ and H+ is ______ to _____.
oxidized, Met+, reduced, H2
41
To name a metal alkoxide:
Name the cation first, followed by the name fo the anion. The name of the anion is derived from the number of carbon atoms and their arrangement followed by -oxide.
42
Alcohols can be converted to salts by reaction with bases _____ than alkoxide ions.
stronger
43
What is an example of a base that converts alcohols to salts?
NaH
Hydride is the conjugate base of H2, making it extremely strong
44
Reactions of sodium hydride with compounds containing acidic hydrogens are ______ and driven to completion by:
irreversible
the formation of H2, which is give off as a gas
45
A common theme for reactions of alcohols is the conversion of:
the -OH group into a better leaving group by protonation and/or replacement with a halogen or other group.
46
Alcohols can be converted to haloalkanes by reaction with:
HCl, HBr, HI, PBr3, SOCL2, or SOBr2
47
The HX reactions work best for tertiary alcohols when:
they involve a carbocation intermediate
48
PBR3, SOCL2, or SOBr2 react well with:
secondary and primary alcohols
49
PBR3, SOCl2, and SOBr3 reactions with secondary and primary alcohols involve ___ displacement, so:
SN2
inversion of stereochemistry is seen when they OH group is bonded to a chiral center
50
Alcohols react with ______ to give alkyl sulfonates.
sulfonyl chlorides
51
The sulfonate group is a _____ leaving group analogous to _________, so alkyl sulfonates can take part in __________.
good, a halogen atom, substitution and elimination reactions
52
_______ alcohols react rapidly with HCl, HBr, and HI.
Tertiary
53
Mixing a low-molecular-weight, water-soluble tertiary alcohol with concentrated HCl for a few minutes at room temp. results in:
conversion of the alcohol to a chloroalkane
54
Low-molecular-weight, water soluble _____ and _____ alcohols are unreactive when mixed with HCl for a few minutes at room temp.
primary, secondary
55
Water-insoluble tertiary alcohols are converted to tertiary halides by:
bubbling gaseous HX through a solution of the alcohol dissolved in diethyl ether or THF
56
Water-insoluble react very _____ when gaseous HX is bubbled through a solution of the alcohol in diethyl ether or THF.
slowly
57
Many secondary alcohols give at least some _______ product when reacted with HX, showing evidence of __________.
rearrangement, carbocation intermediates
58
Primary alcohols with extensive beta-branching give large amounts of ______________ when reacted with HX.
a product derived form rearrangement
59
What is the relative ease of reaction of alcohols with HX?
Tertiary > secondary > primary
60
Based on __________ and ________, chemist propose an SN1 mechanism for the conversion of ________ and _______ to haloalkanes by concentrated HX, with the formation of __________.
the relative ease of reaction,
the occurrence of rearrangements,
tertiary and secondary,
a carbocation intermediate
61
What are the steps of the mechanism for the reaction of a tertiary alcohol with HBr?
1) add a proton
2) break a bond to give stable molecules or ions
3) make a new bond between a nucleophile and an electrophile
62
Describe step one of the mechanism for the reaction of a tertiary alcohol with HBr: add a proton
Rapid and reversible proton transfer from H3O+ to the -OH group of the alcohol gives an oxonium ion, which converts -OH, a poor leaving group, into -OH2+, a better leaving group
63
Describe step 2 of the reaction of a tertiary alcohol with HBr: break a bond to give stable molecules or ions
Loss of water gives a tertiary carbocation intermediate
64
Describe step 3 of the reaction of a tertiary alcohol with HBr: make a new bond between a nucleophile and an electrophile
Reaction of the tertiary carbocation (an electrophile) with bromide ion (a nucleophile) gives the haloalkane
65
Primary alcohols with no beta-branching react with HX by:
an SN2 mechanism
66
What is the rate determining step of the reaction of a primary alcohol with no beta-branching with HX?
When the halide ion reacts at the carbon bearing the oxonium ion to displace H2O and for the C-X bond
67
What are the steps for the mechanism of the reaction of a primary alcohol with HBr (SN2)?
1) add a proton
2) make a new bond between a nucleophile and an electrophile and simultaneously break a bond to give stable molecules or ions
68
Describe step one of the reaction of a primary alcohol with HBr (SN2): add a proton
Rapid and reversible proton transfer gives an oxonium ion, which transforms -OH, a poor leaving group, into -OH2+, a better leaving group
69
Describe step two of the reaction of a primary alcohol with HBr (SN2): make a new bond between a nucleophile and an electrophile and simultaneously break a bond to give stable molecules or ions
Nucleophilic displacement of H2O by Br- gives the bromoalkane
70
Primary alcohols with extensive beta-branching react by a mechanism involving:
What is this reaction classified as and why?
formation of a tertiary carbocation intermediate by simultaneous loss of H2O and migration of an alkyl group
Classified as SN1, because the rate-determining step of the transformation involves only one reactant.
71
What are the steps of the mechanism for rearrangement upon treatment of a CH3C(CH3)2CH3OH (neopentyl, a primary alcohol with extensive beta-branching) with HCl?
1) add a proton
2) 1,2 shift and simultaneously break a bond to give stable molecules or ions
3) make a new bond between a nucleophile and an electrophile
72
Describe step 1 for rearrangement upon treatment of a CH3C(CH3)2CH3OH (neopentyl, a primary alcohol with extensive beta-branching) with HCl: add a proton
Rapid and reversible proton transfer gives an oxonium ion
73
Describe step 2 for rearrangement upon treatment of a CH3C(CH3)2CH3OH (neopentyl, a primary alcohol with extensive beta-branching) with HCl: 1,2 shift and simultaneously break a bond to give stable molecules or ions
Two changes take place simultaneously in this step; the C-O bond breaks, and a methyl group with its pair of bonding electrons migrates o the site occupied by the departing H2O group. The result is the loss of H2O and the formation of a tertiary carbocation
74
Describe step 3 for rearrangement upon treatment of a CH3C(CH3)2CH3OH (neopentyl, a primary alcohol with extensive beta-branching) with HCl: make a new bond between a nucleophile and an electrophile
Reaction of the tertiary carbocation (an electrophile) with chloride ion (a nucleophile) gives the tertiary haloalkane
75
Alcohols react with PBr3 to:
initially displace Br- to give a protonated dibromophosphite intermediate, which is displaced from the backside by Br- to give the bromoalkane
76
Although rearrangement sometimes occurs with PBr3, the extent is considerably less than:
that with HBr
77
What are the steps of the mechanism for the reaction of a primary alcohol with PBr3?
Step one and two are the same idea:
make a new bond between a nucleophile and an electrophile and simultaneously break a bond to give stable molecules or ions
78
Describe step one for the reaction of a primary alcohol with PBr3:
Nucleophilic displacement on phosphorous by the oxygen atom of the alcohol gives a protonated dibromophsophite group, which converts -OH to a good leaving group (OHPB2+, rather than OH2+)
79
Describe step 2 for the reaction of a primary alcohol with PBr3:
Nucleophilic displacement of the protonated dibromophosphite group by bomide ion gives the bromoalkane
80
In the reaction of a primary alcohol with PBr3, the two bromine atoms on phosphorous are replaced in similar reactions, giving:
three moles of RBr and one moles of H3PO3 (phosphorous acid)
81
Alcohols react with SOCl2 to:
initially give an alkyl chlorosulite intermediate, which is displaced from the backside by Cl- to give the chloroalkane
82
What is often the method of choice for converting a primary or secondary alcohol to an alkyl chloride or alkyl bromide?
Reaction with SOCl2
83
What is the name for SOCl2?
Thionyl chloride
84
When primary and secondary alcohols react with SOCl2, yields are ____ and rearrangements are _____ observed.
high, rarely
85
Thionyl bromide (SOBr2) can be used to convert an alcohol to:
a bromoalkane
86
Reactions with SOCl2 and SOBr2 are commonly carried out in the presence of _______.
pyridine or a tertiary amine
87
What are the functions of the tertiary amine in the SOCl2 and SOBr2 reactions?
It catalyzes the reaction by forming a small amount of the alkoxide in equilibrium. It neutralizes the HCl or HBr generated in the reaction as well, which prevents side reactions
88
Thionyl halide reactions with alcohols are ________, occurring with ___________.
stereoselective, inversion of configuration
89
Alcohols also react with compounds calle sulfonyl chlorides to form:
alkylsulfonites
90
Sulfonyl chlorides are derived from ________, which are comparable in strength to _______.
sulfonic acids, sulfuric acid
91
The sulfonate ion is a very _____ base and _____ anion.
weak, stable
92
The sulfonate ion is a ______ leaving group.
very good
93
Two of the most commonly used sulfonyl chlorides are:
p-toluenesulfony chloride (tosyl chloride, TsCl) and methanesulfonyl chloride (mesyl chloride, MsCl)
94
Treating ethanol with TsCl in the presence of pyridine gives:
______ is added to catalyze the reaction and to _____ HCl formed as a byproduct.
ethyl p-toluenesulfonate
pyridine, neutralize
95
In formation of either a tosylate or mesylate, the reaction does not affect:
the O-H bond
96
If the carbon bearing the -OH group is a chiral center, sulfonate ester formation takes place with:
retention of configuration
97
Tosylate (OT) or mesylate (OM) groups are _____ leaving groups.
very good
98
What is step one of the mechanism for the reaction via a tosylate?
Treat the alcohol with p-toluenesulfonyl chloride in pyridine to form a tosylate with retention of configuration as the chiral center is not involved in this step.
99
What is step two of the mechanism for the reaction via a tosylate?
Treat the OT with a good nucleophile to displace -OT in an SN2 reaction.
100
Backside attack is not possible for an _______ leaving group of a cyclohexane ring.
What does this cause?
equatorial
This causes the requirement of a ring flip for X- displacement can occur.
101
Dehydration reactions
Involves the elimination of water from adjacent carbon atoms
102
Treatment of alcohols with strong acids leads to:
dehydration to give an alkene
103
_________ rule is followed in the reaction of alcohols with strong acids.
Zaitsev's
104
The principle of microscopic reversibility
The sequence of transition states ad reactive intermediates (that is, the mechanism) for any reversible reaction must be the same, but in reverse order for the reverse reaction as for the forward reaction.
105
In acid-catalyzed dehydration reactions, when isomeric alkenes are possible, the major product is:
the more substituted alkene
106
In acid-catalyzed dehydration reactions, rearrangements are common with ______ alcohols and _______________.
secondary, primary alcohols with extensive beta-branching
107
The mechanism for acid-catalyzed dehydration is the reverse of:
acid-catalyzed hydration of an alkene
108
What acids are most common in dehydration reactions, and what other element is involved?
85% H3PO4 and 85% H2SO4, heat
109
The ease of acid catalyzed dehydration of alcohols is:
Tertiary > secondary > primary
110
What are the steps for the mechanism of acid-catalyzed dehydration (E1)?
1) add a proton
2) break a bond to give stable molecules or ions
3) take a proton away
111
Describe step one for the mechanism of acid-catalyzed dehydration (E1): add a proton
Proton transfer from H3O+ to the OH group gives an oxonium ion
112
Describe step 2 for the mechanism of acid-catalyzed dehydration (E1): break a bond to give stable molecules or ions
Breaking the C-O bond and loss of H2O gives a secondary carbocation intermediate (in the case of a secondary alcohol)
113
Describe step 3 for the mechanism of acid-catalyzed dehydration (E1): take a proton away
Proton transfer from a carbon adjacent to the positively charged carbon to H2O gives the alkene. The electrons of the C-H sigma bond become the electrons of the pi bond
114
Dehydration of primary and secondary alcohols is often accompanied by ________.
rearrangement
115
Based on ______________ and ___________, particularly among primary and secondary alcohols, chemist propose a ______-step mechanism for acid catalyzed dehydration of secondary and tertiary alcohols.
the relative rates of dehydration of alcohols, the prevalence of rearragement, three
116
The three-step mechanism for acid catalyzed dehydration of secondary and tertiary alcohols involved formation of a carbocation in the _________ and therefore is classified as __________.
rate-determining step, an E1 mechanism
117
Primary alcohols with little or no beta-branching undergo acid-catalyzed dehydration to give:
a terminal alkene and rearranged alkenes (don't forget trans and cis isomers of the internal alkenes)
118
We account for the mechanism of the formation of terminal and rearranged alkenes in acid-catalyzed dehydration of primary alcohols with little or no beta-branching through:
a combination of E1 and E2 mechanisms
119
What are the steps for the mechanism of acid-catalyzed dehydration of an unbranched primary alcohol?
1) add a proton
2 E2) take a proton away and simultaneously break a bond to give stable molecules or ions
2 E1) 1,2 shift and simultaneously break a bond to give stable molecules or ions
3 E1) take a proton away
120
Describe step 1 for the mechanism of acid-catalyzed dehydration of an unbranched primary alcohol: add a proton
Proton transfer from H3O+ to the OH group gives an oxonium ion
121
Describe step 2 for the E2 mechanism of acid-catalyzed dehydration of an unbranched primary alcohol: take a proton away and simultaneously break a bond to give stable molecules or ions
Simultaneous proton transfer to solvent and loss of H2O gives the C=C bond of the terminal alkene
122
Describe step 2 for the E1 mechanism of acid-catalyzed dehydration of an unbranched primary alcohol: 1,2 shift and simultaneous break of a bond to give stable molecules or ions
Simultaneous shift of a hydride ion from the beta-carbon to the alpha-carbon and loss of H2O gives a carbocation intermediate
123
Describe step 3 of the E1 mechanism for acid-catalyzed dehydration of an unbranched primary alcohol: take a proton away
Transfer of a proton from a carbon adjacent to the carbocation to solvent gives the rearranged alkenes
124
Both the alkene hydration and alcohol dehydration reactions are ________.
reversible
125
Large amounts of water (dilute aqueous acid) favors ________ formation.
alcohol
126
Scarcity of water (conc. acids) favors ______ formation.
alkene
127
Some compounds containing OH groups on adjacent atoms (glycols) undergo a characteristic reaction in acid to generate:
a rearranged aldehyde or ketone product
128
Dehydration of glycol involves: formation of a carbocation intermediate, rearrangement, and loss of H+ to give an aldehyde or a ketone.
formation of a carbocation intermediate, rearrangement, and loss of H+ to give an aldehyde or a ketone
129
What are glycols also called?
vicinal diols
130
What is the characteristic reaction of glycols called?
The Pinacol Rearrangement
131
What are the steps of the mechanism for the conversion of pinacol to pinacolone (a pinacol rearrangement)?
1) add a proton
2) break a bond to give stable molecules or ions
3) 1,2 shift
4) take a proton away
132
Describe step 1 for the mechanism for the conversion of pinacol to pinacolone (a pinacol rearrangement): add a proton
Proton transfer from the acid catalyst to one of them-OH group gives an oxonium ion
133
Describe step 2 for the mechanism for the conversion of pinacol to pinacolone (a pinacol rearrangement): break a bond to give stable molecules or ions
Loss of H2O from the oxonium ion gives a tertiary carbocation intermediate
134
Describe step 3 for the mechanism for the conversion of pinacol to pinacolone (a pinacol rearrangement): 1,2 shift
Migration of a methyl group from the adjacent carbon with its bonding electrons gives a new, more stable, resonance-stabilized cation intermediate.
135
Describe step 4 for the mechanism for the conversion of pinacol to pinacolone (a pinacol rearrangement): take a proton away
Proton transfer to solvent gives pinacolone
136
Studies of unsymmetrical vicinal diols reveal that:
the -OH group that becomes protonated and leaves is the one that gives rise to a more stable carbocation
137
Primary alcohols are oxidized by aqueous H2CrO4 (chromic acid) to give:
carboxylic acids
138
Jones reagent
A solution of chromic acid in aqueous sulfuric acid
139
What does the process of oxidation of a primary alcohol using a primary alcohol involve?
Initial aldehyde formation, followed by conversion to an aldehyde hydrate that is further oxidized to the carboxylic acid
140
Secondary alcohols are oxidized to ______ by chromic acid.
ketones
141
What is step one of the mechanism for chromic acid oxidation of an alcohol?
Reaction of the alcohol and chromic acid give an alkyl chromate by a mechanism similar to that for the formation of a carboxylic ester.
142
What is step two of the mechanism for chromic acid oxidation of an alcohol?
Break bonds to give stable molecules or ions
Reaction of the alkyl chromate with a base results in cleavage of a C-H bond, formation of the carbonyl group, and reduction of chromium (VI) to chromium (IV). This is the oxidation-reduction step.
143
In the second step of chromic acid oxidation, it is not the aldehyde that is _________, but rather the aldehyde _______ formed by addition of a water molecule to the aldheyde carbonyl group
oxidized, hydrate
144
The hydration step of chromic acid oxidation is crucial because:
it converts the aldehyde carbonyl into two hydroxyl groups. Chromic acid can only react with -OH to for an alkyl chromate ester, not a carbonyl
145
The hydration process of chromic acid oxidation is catalyzed by:
acid
146
Although equilibrium favors the aldehyde in chromic acid oxidation, enough _____ is made to complete the reaction.
hydrate
147
The form of Cr(VI) most commonly used for oxidation of a primary alcohol to an aldehyde is prepared by:
dissolving CrO3 in aqueous HCl and adding pyridine to precipitate pyridinium chlorochromate (PCC) as a solid
148
PCC is not only selective for the ______ of primary alcohols, but has little effect of C=C bonds or other easily ________ functional groups.
oxidation, oxidized
149
PCC does not oxidize aldehydes further because:
the PCC reagent is not used in water but rather in an organic solvent, usually CH2Cl2
150
Without water, the product aldehyde:
is not in equilibrium with the aldehyde hydrate
151
PCC is used to oxidize primary alcohols to _______.
aldehydes
152
Both PCC and H2CrO4 can be used for the oxidation of a _______ alcohol to a ketone.
secondary
153
Why is the Swern Oxidation used?
The jones reagent and PCC are toxic
154
What is the oxidizing agent in the Swern oxidation?
Chlorosulfonium salt, which is generated by the reaction of DMSO with oxalyl chloride
155
Slow addition of the alcohol at ____ temp. to the chlorosulfonium salt, followed by the addition of __________, yields the product.
low, a tertiary amine
156
Using the Swern oxidation, primary alcohols are cleanly oxidized to _______, secondary alcohols yield ______, and tertiary alcohols are unreactive.
aldehydes, ketones
157
What is step one for the mechanism of the Swern oxidation, starting at the point of the chlorosulfonium ion?
The reaction of the chlorosulfonium with an alcohol creates an alkylsulfonium ion and HCl.
158
What is step two for the mechanism of the Swern oxidation, starting at the point of the chlorosulfonium ion?
Take a proton away
The addition of a tertiary amine leads to a deprotonation of the methyl adjacent to the cationic sulfur, leading to what is referred to as an alkoxysulfonium ylide
159
What is step three for the mechanism of the Swern oxidation, starting at the point of the chlorosulfonium ion?
Take a proton away while simultaneously breaking a bond so that stable molecules or ions are created.
The carbanion performs an intramolecular proton transfer that induces cleavage of the alkoxysulfonium ylide into dimethylsulfide and the oxidized product
160
Dess-Martin periodinane (DMP)
A hypervalent iodine compound that is used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones
161
What is step one of Dess-Martin oxidation?
Reaction of an alcohol with DMP gives diacetoxyalkoxy periodinane
162
What is step 2 of the Dess-martin oxidation?
Take a proton away while simultaneously breaking a bond so that stable molecules or ions are created
Deprotonation of the hydrogen on the coordinated alkoxy group leads to a reduction of the iodine, expulsion of acetate, and the oxidized aldehyde or ketone product
163
HIO4 reacts with a glycol to form:
A five-membered cyclic periodate intermediate that undergoes carbon-carbon bond cleavage to form two carbonyl groups
164
The major use of periodic acid (H5IO6) or alternatively HIO4 and 2H2O is for:
The cleavage of glycol to two carbonyl groups
165
Periodic acid is reduced to
iodic acid
166
What is step 1 for the mechanism of oxidation of a glycol by periodic acid?
Reaction of a glycol with periodic acid gives a five-membered cyclic periodate
167
What is step 2 for the mechanism of oxidation of a glycol by periodic acid?
Break bonds to give stable molecules or ions
Redistribution of valence electrons within the cyclic periodate gives HIO3 and two carbonyl groups.
168
What is a result of valence electron redistribution within cyclic periodate?
An oxidation of the organic component and a reduction of the iodine-containing component
169
HIO4 oxidations are restricted to:
glycols that can form five-membered cyclic periodate
170
Thiol
A sulfur analog of an alcohol. It contains an -SH group bonded to an sp^3 hybridized carbon
171
Thiols are named in the same manner as alcohols, but:
the suffix -e of the parent alkane is retained and -thiol is added
172
In compounds containing other functional groups of higher precedence, the presence of -SH is indicated by:
the prefix sufanyl-
173
Because the S-H bond of thiols are almost _______, the physical properties are more like:
nonpolar
those of hydrocarbons of comparable molecular weight
174
Thiols are _____ acidic than alcohols
more
175
Thiols are oxidized to give:
disulfides, sulfinic acids, and sulfonic acids
176
In older nomenclature, thiols were often referred to as ______.
mercaptans
177
What does mercaptan mean?
Mercury catching
178
Why were thiols called mercaptans?
They react with Hg2+ in aqueous solution to give sulfide salts as insoluble precipitates
179
The location of the thiol takes precedence over:
alkyl groups and halogens
180
-OH takes precedence over -SH in both _____ and _____.
numbering, naming
181
What is the most outstanding physical characteristic of low-molecular-weight thiols?
Their stench
182
Thiols have ____ boiling points and ____ soluble in water and other polar solvents than alcohols of comparable molecular weight
low, less
183
The most common preparation of thiols, ____, depends on the high _______ of the hydrosulfide ion.
RSH, nucleophilicity
184
The reaction of HS- with a haloalkane gives a _____
thiol
185
The reaction of HS- with a haloalkane proceeds through a ___ mechanism.
SN2
186
The reaction of HS- and a haloalkane is most useful for preparation of thiols from _______ haloalkanes.
primary
187
Thiols cannot be formed from _______ haloalkanes.
tertiary
188
Thiols have a pKa of _______
10-11
189
HS- is _____ acidic than water
more
190
Why are thiols more acidic than alcohols?
Sulfur, a third period element, is larger than oxygen, a second period element. The negative charge on an alkylsulfide ion (RS-) is delocalized over a larger area, and is therefore more stable than an alkoxide ion.
191
Thiols are sufficiently strong acids so that when dissolved in NaOH, they are converted completely to _________.
alkylsulfide salts
192
To name salts of thiols:
Give the name of the cation first, followed by the name of the alkyl group to which is attached the suffix -sulfide
193
Oxidation of thiols by weak oxidizing agents such as O2 and I2 gives:
disulfides
194
Many of the chemical properties of thiols stem from the fact that the sulfur atom of a thiol is:
oxidized easily to several higher states
195
Thiols are ________ nucleophiles
moderate
196
Thiols rank as ______ nucleophiles in both their neutral and anionic states as compared to alcohols and alkoxides.
better
