Chapter 10 Flashcards
alcohols are important because they can be converted into many other types of compounds, including …, .., …, …, …, and … Not only can alcohols be converted to these compounds, but these compounds can also be converted to alcohols
alkenes; haloalkanes; aldehydes; ketones; carboxylic acids; esters
the functional group of an alcohol is an … (…) group bonded to an … hybridized carbon. The oxygen atom of an alcohol is also … hybridized
OH; hydroxyl; sp^3; sp^3
the location of the OH group takes precedence over … and … atoms in numbering the parent chain
alkyl groups; halogen atoms
common names for alcohols are derived by … bonded to OH and then adding the word …
naming the alkyl group; alcohol
we classify alcohols as primary, secondary, tertiary, depending on whether the OH group is on a
primary, secondary, or tertiary C
In the IUPAC system, a compound containing two hydroxyl groups is named as a …, one containing three hydroxyl groups as a …, and so on
diol; thiol
compounds containing hydroxyl groups on adjacent C are often referred to as
glycols
Compounds containing OH and C=C groups are often referred to as … bc of the presence of the C-C double bond.
unsaturated alcohols
the parent alkane is numbered to give the … the lowest possible number for alcohols
OH
bc of the presence of the polar OH group, alcohols are
polar compounds
the attraction between the positive end of one dipole and the negative end of another is called ..
dipole-dipole interaction
when the positive end of one of the dipoles is a hydrogen atom bonded to O or N and the negative end of the other dipole is an O or N atom, the attractive interaction between dipoles is particularly strong and is given the special name of
H-bonding
An O-H H-bond is considerably … than O-H covalent bond
weaker
the alcohols have the higher bps bc more E is needed to overcome the attractive forces of … between their polar OH groups. The presence of additional hydroxyl groups in a molecule further …
H-bonding; increases the extent of H-bonding
Bc of increased dispersion forces between larger molecules, bps of all types of compounds, including alcohols, increase with
increasing molecular weight
Bc alcohols can interact by H bonding with water, they are more … in water than alkanes and alkenes of comparable molecular weight.
soluble
as molecular weight increases, the physical properties of alcohols become more like those of … of … Higher molecular weight alcohols are much less … in water bc of the increase in size of the hydrocarbon portion of their molecules
hydrocarbons; comparable molecular weight; soluble;
alcohols can function as both … and …
weak acids; weak bases
in dilute aqueous solution, only … is more acidic than water
methanol
… has about the same acidity as water. higher-molecular-weight, water-soluble alcohols are … than water
ethanol; slightly weaker acids
although alcohols have some acidity, they are not strong enough acids to react with … such as sodium bicarbonate or sodium carbonate
weak bases
for simple alcohols like methanol and ethanol, acidity depends primarily on the … and … of the … by water molecules
degree of solvation; stabilization; alkoxide ion
as the bulk of the alkyl group bonded to O increases, the ability of water molecules to solvate the alkoxide ion
decreases
in the presence of strong acids, the O atom of an alcohol is a … and reacts with an … by … to form an … ion
base; acid; proton transfer; oxonium
an important mechanistic theme in many of the rxns of alcohols is that the OH group, a poor leaving group, reacts with protons or a variety of strong electrophiles to create … or analogous group, a much better …, enabling subsequent .. or … rxns to take place
OH2+; leaving group; substitution; elimination
Alcohols react with Li, Na, K, and other active metals to liberate … and form … In this oxidation/reduction rxn, Na is oxidized to … and H+ is reduced to …
hydrogen; metal alkoxides; Na+; H2
alkoxide ions are nearly the same/somewhat stronger bases than the … ion
hydroxide ion
alcohols can also be converted to salts by rxn with bases stronger than …
alkoxide ions
rxns of sodium hydride with compounds containing acidic hydrogens are … and …. by the formation of H2, which is given off as a gas
irreversible; driven to completion
conversion of an alcohol to a haloalkane involves substitution of … for … at a saturated carbon. the most common reagents for this conversion are the …. (HCl, HBr, and HI) and certain … (PBr3, SOCl2, SOBr2)
halogen; OH; halogen acids; inorganic halides
… alcohols react rapidly with HCl, HBr, and HI
tertiary
low molecular weight, water soluble primary and secondary alcohols are … when being reacted with HCl at room temp
unreactive
primary and secondary alcohols are converted to ….. and … by treatment with hydrobromic and hydroiodic acids
bromoalkanes; iodoalkanes
many secondary alcohols give at least some … product, evidence for the formation of … intermediates during their rxn
rearranged; carbocation
primary alcohols with extensive beta branching give large amounts of a product derived from
rearrangement
based on observations of the relative ease of rxn of alcohols w/ HX and the occurrence of rearrangements, chemists propose an … mechanism for the conversion of tertiary and secondary alcohols to haloalkanes by concentrated HX, with the formation of a carbocation intermediate
SN1
(rxn of a tertiary alcohol with HBr-SN1)
1. add a proton: while we often show HBr as the acid present in solution, the actual acid involved in this rxn is … formed by … in aqueous solution . Rapid and reversible proton transfer from H3O+ to the OH group of the alcohol gives an … ion, which converts OH, a poor leaving group, into …, a better leaving group
H3O+; dissocation of HBr; oxonium; OH2+
(rxn of a tertiary alcohol with HBr-SN1)
2. break a bond to give stable molecules/ions: loss of … gives a tertiary carbocation intermediate
water
(rxn of a tertiary alcohol with HBr-SN1)
3. make a new bond between a nu and an electrophile: rxn of the tertiary carbocat with Br- gives the
haloalkane
primary alcohols with no beta branching react with HX by an … mechanism
SN2
(rxn of a primary alcohol with HBr-SN2)
- add a proton: rapid and reversible proton transfer gives an … ion, which transforms OH, a poor Lv, into …, a better Lv
- make a new bond between a nucleophile and an electrophile and simultaneoulsy break a bond to give stable molecules/ions. … of water by Br- gives the bromoalkane
nucleophilic displacement
for primary alcohols with extensive beta branching, it is difficult, if not impossible, for rxn to occur by … of H2O from the primary C. Furthermore, formation of a primary carbocation is also difficult, if not impossible. Instead, primary alcohols with extensive beta branching react by a mechanism involving formation of a … intermediate by simultaneous … and … Bc the rate-determining step of this transformation involves only one reactant, namely the protonated alcohol, it is classified as an …r xn
direct displacement; tertiary carbocation; loss of water; migration of an alkyl group; SN1
preparation of haloalkanes by treatment of ROH with HX is most useful for … and … alcohols. Bc of the possibility of …, this process is less useful for … alcohols and for … alcohols w/ extensive …
primary; tertiary; rearrangement; secondary; primary; branching on the beta C
an alternative method for the synthesis of bromoalkanes from primary and secondary alcohols is through the use of …
phosphorus tribromide (PBr3)
although rearrangement sometimes occurs with PBr3, the extent is considerably less than that with
HBr
(rxn of a primary alcohol with PBr3)
- make a new bond between a nucleophile and an electrophile and simultaneously break a bond to give stable molecules/ions: nucleophilic displacement on phosphorus by the … atom of the alcohol gives a protonated … group, which converts OH into a good Lv
- make a new bond between a nu and an electrophile and simultaneoulsy break a bond to give stable molecules/ions: nucleophilic displacement of the protonated dibromophosphite group by bromide ion gives the bromoalkane. The other two bromines on P are replaced in similar rxns, giving … moles of RBr and … moles of phosphorous acid
O; dibromophosphite; 3; 1
the most widely used reagent for the conversion of primary and secondary alcohols to chloralkanes is … Yields are high and … are seldom observed. the byproducts are HCl and SO2
thionyl chloride, SOCl2; rearrangements
…. can be used to convert an alcohol to a bromoalkane
thionyl bromide, SOBr
rxns with SOX2 are most commonly carried out int he presence of … or a …, which … the rxn by forming a small amount of the … in equilibrium. this is more reactive than the alcohol as a nucleophile. In addition, the amine neutralizes the … or … generated during the rxn and prevents unwanted side rxns
pyridine; tertiary amide; catalyzes; alkoxide; HCl; HBr
a particular value of thionyl halides is that their rxn with alcohols is …; it occurs with …
stereoselective; inversion of config
a key feature of the rxn of an alcohol with thionyl chloride is the formation of an …, which converts hydroxide into a … that now contains a good Lv. If the rxn betweent he alcohol and thionyl chloride is carried out at 0 degrees C or below, the alkyl chlorosulfite can be isolated
alkyl chlorosulfite; chlorosulfite
alcohols also rxt with compounds called … to form alkylsulfonates
sulfonyl chlorides
a sulfonate anion is a very … base and … anion; therefore, it is a very good … in nucleophilic sub rxns
weak; stable; leaving group
in formation of either a tosylate or a mesylate the rxn involves breaking the … of the alcohol; it does not affect the … bond in any way. If the C bearing the OH group is a chiral center, … formation takes place with … of config
O-H; C-O; sulfonate ester; retention
a particular advantage of sulfonate esters is that through their use, a hydroxyl group, a very poor leaving group, can be converted to a .. or … group, often shown as OTs and OMs, respectively. Both are very good Lvs readily displaced by nucleophilic substitution
tosylate; mesylate
an alcohol can be converted to an alkene by
dehydration
dehydration is most often brought about by … the alcohol with either 85% phosphoric acid or concentrated sulfuric acid. Primary alcohols are the most … to dehydrate and generallly require heating in … at temperatures as high as …
Secondary alcohols undergo acid-catalyzed dehydration at somewhate … Acid-catalyzed dehydration of tertiary alcohols often requires temperatures only slightly …
difficult; concentrated sulfuric acid; 180 degrees C; lower temperatures; above room temp
when isomeric alkenes are obtained in acid-catalyzed dehydration of an alcohol, the … alkene generally predominates
more substituted
dehydration of primary and secondary alcohols is often accompanied by
rearrangement
acid-catalyzed dehydration of secondary and tertiary alcohols involves formation of a … in the rate-determining step and therefore is classified as an … mechanism
carbocation; E1
(acid-catalyzed dehydr-E1)
- add a proton: proton transfer forms OH2, a better Lv
- break a bond to give stable molecules/ions: breaking of the … bond and loss of … gives a C+ intermediate
- take a proton away: proton transfer from a C adjacent to the … to H2O gives the alkene. In this step, the e- of the C-H sigma bond become the e- of the pi bond
C-O; H2O; positively charged C;
primary alcohols with liitle/no beta branching undergo acid-catalyzed dehydration to give a … and .. We account for the formation of these products by a combination of … and … mechanisms
terminal alkene; rearranged alkenes; E1 and E2
As in other cases of acid-catalyzed dehydration of alkenes, the … rule applies, and the more substituted alkene predominates
Zaitsev
(acid-catalyzed dehydration of an unbranched primary alcohol)
- add a proton to give the oxonium ion
- take a proton away and simultaneously break a bond to give stable molecules/ions: simultaneous proton transfer to solvent and loss of water gives the C=C of the terminal alkene
- 1,2 shift and simultaneously break a bond to give stable molecules/ions : simultaneous shift of a … ion from the beta C to the alpha C and loss of H2O gives a …
- take a proton away: transfer of a proton from a C adjacent to the carbocat to … gives the rearranged alkenes
hydride; carbocat intemediate; solvent
both the alkene hydration and the alcohol dehydration rxns are … and represent … of …
reversible; different directions; the same process
for the hydration/dehydration equilibrium, large amounts of water favors … formation, whereas scarcity of water or experimental conditions where water is remove favor … formation
alcohol; alkene
principle of microscopic reversibility: according to this principle, the sequence of transition states and reactive intermediates for any reversible rxn must be …, but in …., for the reverse rxn as for the forward rxn
the same; reverse order
compounds containing hydroxyl groups on two adjacent C atoms are called … or …
vicinal diols; glycols
such compounds (glycosl) can be synthesized by a variety of methods, including
oxidation by OsO4
acid-catalyzed dehydration of glycols involves dehydration to form a … and migration of a … group from one C to an adjacent C. Acid-catalyzed conversion of a pinacol to pinacolone si an example of a type of rxn called the …
ketone; methyl; pinacol rearrangement
(pinacol rearrangement)
- add a proton to form OH2+, a better Lv
- break a bond to give stable molecules/ions: loss of water from oxonium gives a carbocat intermediate
- 1,2 shift: migration of a methyl group from the adjacent carbon with its bonding e- gives a new, more stable … intermediate. 4. take a proton away: proton transfer to … gives …
resonance-stabilized cation; solvent; pinacolone
the pinacol rearrangement is … for all glycols
general
studies of unsymmetrical vicinal diols reveal that the OH group that becomes protonated and leaves is the one that gives rise to the more
stable carbocation
oxidation of a primary alcohol gives an … or a …, depending on conditions. Secondary alcohols are oxidized to …, Tertiary alcohols …
aldehye; carboxylic acid; ketones; are not oxidized
one reagent used in the lab for the oxidation of a primary alcohol to a carboxylic acid is …, … A solution of this acid in aqueous sulfiuric acid is known as the … reagent
chromic acid; H2CrO4; Jones
oxidation by chromic acid is commonly carried out by dissolving organic compounds in acetone and then adding a stoichiometric amount of … to complete it
Jones reagent
secondary alcohols are oxidized to … by chromic acid
ketones
tertiary alcohols are resistant to oxidation because the C bearing the OH is already bonded to three C atoms and therefore cannot form an additional … bond. Thus,t he prereq for the oxidation of an alcohol to an aldehyde/ketone is at least one … on the C bearing the OH
C-O; H
(chromic acid oxidation of an alcohol)
1. rxn of the alcohol and chromic acid gives an … by a mechanism similar to that for the formation of a carboxylic ester.
2. take a proton away and simultaneously break bonds to give stable molecules/ions: rxn of the alkyl chromate with a base results in cleavage of a … bond, formation of the … group, and reduction of chromium (VI) to …
This step is the … step; C undergoes a 2-e- oxidation and Cr undergoes a 2-e- reduction to Cr4, whicht hen participates in further oxidations by a similar mech and eventually is transformed to Cr3
alkyl chromate; C-H; carbonyl; chromimum (IV); oxidation-reduction
in aqueous chromic acid, a primary alcohol is oxidized first to an … and then to a … In the second step, it is not the aldehyde that is oxidized, but rather the … formed by addition of a molecule of water to the ..An OH of the aldehyde hydrate reacts with chromic acid to complete the oxidation of the aldehyde to a ….
aldehyde; carboxylic acid; aldehyde hydrate; aldehyde carbonyl group (hydration); carboxylic acid
the hydration step is critical bc it converts the aldehyde carbonyl tnto two … groups. Chromic acid can only react with OH to form an alkyl chromate ester, not a carbony. The hydration process is catalyzed by …, and although equilibrium favors the aldehyde, enough hydrate is made to complete the rxn
hydroxyl; acid;
the form of Cr(VI) most commonly used for oxidation of a primary alcohol to an aldehyde is prepared by dissolving CrO3 in aqueous HCla nd adding pyridine to precipitate … as a solid. PCC is not only selective for the oxidation of primary alcohols to … but also has little effect on C=C bonds or other easily … functional groups
pyridinium chlorochromate (PCC); aldehydes; oxidized
PCC does not oxidize aldehydes further bc the reagent is not used in water. without water, the product aldehyde is not in equilibrium with the
aldehyde hydrate
both PCC and H2CrO4 can be used for the oxidation of a secondary alcohol to a
ketone
Swern oxidation uses … as the oxidizing agent
chlorosulfonium salt
with swern, primary alcohols are cleanly oxidized to …, secondary yields …, and tertiary are again … it accomplishes the same transformatiosn as …
aldehydes; ketones; unreactive; PCC
…. also achieves the same transformations as PCC and Swern
Dess-Martin periodinane
hypervalent means a compound with a greater electron count than
predicted by the octet rule
periodic acid … is used for the cleavage of a glycol to two …
H5IO6; carbonyl groups
HIO4 oxidations are restricted to glycols that can form a … Any glycol that can’t is not oxidized by …
five-membered cyclic periodate; periodic acid
the functional group of a thiol is an … (…) gorup bonded to a … hybridized C
SH; sulfhydryl; sp^3
there is considerably more … character in the bonding orbitals of divalent sulfur than there is in those of divalent oxygen
p
thiols are often referred to as …, which means … They react with … in aqueous solution to give … salts as precipitates
mercaptans; mercury capturing; Hg2+; sulfide
the location of the SH group takes precedence over … and … in numbering, but … takes precedence over SH
alkyl groups; halogens; OH
in compounds containing both OH and SH, an SH group is indicated by the prefix …
sulfanyl
because of the very low polarity of the S-H bond, thiols show little association by … Consequently, they have lower … and are less … in water and other polar solvents than alcohols of comparable molecular weights
H-bonding; boiling points; less soluble
the most common preparation of thiols, RSH, depends on the high … of the hydrosulfide ion, HS-
nucleophilicity
rxn of HS- with a haloalkane gives a … the scope and limitations of this rxn are governed by the limitations of the … rxn and by competition between … and … the rxn is most useful for preparation of thiols from … haloalkanes. yields are lower from … halides because of the competing … with tertiary halides … predominates, and the alkene formed by dehydrohalogenation is the major product
thiol; SN2; substitution; beta elimination; primary haloalkanes; secondary; beta elimination rxn; E2
… is much more acidic than water
hydrogen sulfide
thiols are stronger acids than
alcohols
the greater acidity of thiols compared to alcohols can be explained by the fact that sulfur is … than oxygen,, so the negative charge on an RS- ion is … over a larger area and is therefore more … than the negative charge on an alkoxide ion
larger; delocalized; stable
thiols are sufficiently strong acids so that when dissolved in aqueous sodium hydroxide, they are converted completely to
alkylsulfide salts
many of the chemical properties of thiols stem from the fact that the sulfur atom of a thiol is … easily to several higher oxidation states
oxidized
thiols are oxidized to disulfides by
molecular oxygen
thiols are … nucleophiles and thiolates are … nucleophles. they rank as better nucleophiles in both netural and anionic states as compared to … and …, respectively. the reasion si bc S is more … than O, which enhances nucleophilicity. also because the pKa values for thiols are generally …, the anions react with … primarily through an … mechanism rather than an … the reverse is true for …
moderate; good; alcohols; alkoxides; polarizable; less than 11; secondary haloalkanes; SN2; E2
