Chapter 12 Alcohols :
& Phenols
12 1 .
Structure and Properties of Alcohols
·
An alcohol a re compound that possess a hydroxyl group (OH) connect to an sp3-hybridized carbon atom ,
and a re characterized by ending
name i n "ol" on
Λ o애
애
Ethanol Cyclopentan o
Phenol it compound that exhibits -OH group connected directly to a phenyl
is a an
ring
·
-
.
·
substituted phenols are
extremely common in nature
Vomenclature Pheno
Identify the parent Replace the Suffix "e"with "ol" to indicate the presence of alcohol
·
1) and name
애
2) Identify and name the substitutent ~ ~
.
3 Assign a locant to each substitutent Pentane Pentanol
↑ Assemble the substitute
alphabetically Identify the longest chain with
·
-
of group
애 · When
numbering the parent chain of an alcohol ,
the-oH group should
l
G
하
~ 5
receive the lowest number possible
2
ㅣ
s
+ .
· When a chival center is
present , the configuration must be indicated at the
beginning
}
om of the n am e
~ e ·
Cyclic alcohols a re numbered starting at the position bearing the -OH group
(R)- 2-Chloro-3-phenyl-1-proparol So there is n o need to indicate the position of the -OH group , assumed at 2-1
ㄴ 매
λ
Of s
> inol
'
(R)-3
Cyclopentand ,
3-dimethyl eyclopent and 2 methyl-2-propanol
12. 2
Acidity of alcohols and Phenols
_
Acidity of the hydroxyl Functional group
M
· The conjugate base of an alcohol is called alkoxide ion
,
it exhibite a
negative charge on an
oxygen atom .
· A
negative charge on an
oxygen atom is more etable than a
negative charge on a
carbon/nitrogen atom but less stable than
a
negative charge on a
halogen (X)
-
-
ncreasing stability Increasing acidity
>
y. θ
O R *
_
R: R -
Q . :
B -
H R- NH 2 B -
¤ H : 必 -
h
…
Least Stable
↓ must stable
~
45 -
50 35 -
40 1的 -
18 -
b0 -
3 prka
, Reagent for depronating an alcohol
There a re 2 ways to depronate an alcohol , forming an alkoxide ion
2) A
strong base can be used to depronate the alcohol .
A commonly base is Natt ,
because hydride (HO) depronate
the alcohol to generate hydrogen gas :
~ㄱ
NP- + H
Ethanol sodiumtlydale sodium ethoxide Hydrogen gas
b Alternatively , an alwhol can be depronated upon
treatment with Li , Na or K .
These metals react withthe alcohol to liberate
hydrogen gas, producing alkoxide ion
¤'
… →
〜 ¤ N +
芝
-
Converted alcohol upon treatment Hgot
e) into its
corresponding with acid , Such a s
ㅐ
~ θ 0
θ . .
.
거 내
R -
℃ : _ R- -
H
An alkoxide Amalcohol
)
↳ Hzst can be prepared by diluting a
strong acid , such an Ha or HaSUp ,
in water , although there a re other ways to prepare even
milder aqueous acidic condition
Factors
affecting the acidity of alcohols and phenols
significant the
1 Resonance one of the most factors affecting acidity of alcohols and
phenols is resonance
-
매 애
Cyclohexanol phendl
(pka = (2) (pka = (s)
When pheno depronated , the conj bane is stabilized
is .
by resonance
θ
ㅣ
_
出感感速
:O: : 0:
=> This resonance stabilized anion in called
ㄴ
→→ phenolate/phenoxide
↳ Phenol does Not need to depronated with a
very strong
bare like sodium hydride) It can be depronated
by
INn
@ hydroxide
※ :0
⑤⑧ →
⑤ + + h 20
pKa = 15 f .
BKa = 10 0
.
立
飛
, 2
, Induction :
el
〜
os Non => Trichloroethanol is 4 orders of magnitude more acidic than
^
a
디
Ethano I Trichloroethand ethanol ,
because the cors.bane of trichloroethanol is stabilited
(pka = 16 .. 0) (pka = 12 . 2) by the electron-withdrawing effects of the nearby chloride
atoms
The effect
3) solvation effects :
of alkyl branching .
√
-H rot => This difference in
acidity is best explained by a steric effect
…
ethanol tert-Butanol o The ethoxide ion is not
sterically hidered and is therefore more
CpKa = 16 . 0) (pka = 18 .
0)
Solvation Effects
.
3 : To explore the effect of alky/ branching , comparethe acidity of ethanol and tert-butand
〜 √
therefore
o n Λ ol => The ethoxide
sterically hindered and
새
ion i s not is
-
…
Ethand tert-butaho7 more solvated (stabilized) by the solvent , while tert-butanol
CpKa = 16 . 0) ( pKa = 18 03 .
is
sterically hindered and less solvated
Preparation of alcohols via substitution/addition
* Substitution Reaction
、
R -X >
- >
R -
OH
Primcry :
~
i SN2
> XoU
+ Naoh- +
Nad
Tertiary :
→ si ·
~
a - e 〜
t 4 ' ^ + HC
^
애
CMark-addition)
DiluteH2 S04
Additio Reactions Acid-eatalyzed hydration
>
ㅅ
H 20 매
へ 1> Hg(OAC) 2 ,
oxymearation -demecration
ㅣ
>
Λ
2,
NaBHy CMark-addition)
1) BH3 , THF 0m Hydroboration - oxidation
~
7
2 H202 , Naot CAnti-mark)
& Phenols
12 1 .
Structure and Properties of Alcohols
·
An alcohol a re compound that possess a hydroxyl group (OH) connect to an sp3-hybridized carbon atom ,
and a re characterized by ending
name i n "ol" on
Λ o애
애
Ethanol Cyclopentan o
Phenol it compound that exhibits -OH group connected directly to a phenyl
is a an
ring
·
-
.
·
substituted phenols are
extremely common in nature
Vomenclature Pheno
Identify the parent Replace the Suffix "e"with "ol" to indicate the presence of alcohol
·
1) and name
애
2) Identify and name the substitutent ~ ~
.
3 Assign a locant to each substitutent Pentane Pentanol
↑ Assemble the substitute
alphabetically Identify the longest chain with
·
-
of group
애 · When
numbering the parent chain of an alcohol ,
the-oH group should
l
G
하
~ 5
receive the lowest number possible
2
ㅣ
s
+ .
· When a chival center is
present , the configuration must be indicated at the
beginning
}
om of the n am e
~ e ·
Cyclic alcohols a re numbered starting at the position bearing the -OH group
(R)- 2-Chloro-3-phenyl-1-proparol So there is n o need to indicate the position of the -OH group , assumed at 2-1
ㄴ 매
λ
Of s
> inol
'
(R)-3
Cyclopentand ,
3-dimethyl eyclopent and 2 methyl-2-propanol
12. 2
Acidity of alcohols and Phenols
_
Acidity of the hydroxyl Functional group
M
· The conjugate base of an alcohol is called alkoxide ion
,
it exhibite a
negative charge on an
oxygen atom .
· A
negative charge on an
oxygen atom is more etable than a
negative charge on a
carbon/nitrogen atom but less stable than
a
negative charge on a
halogen (X)
-
-
ncreasing stability Increasing acidity
>
y. θ
O R *
_
R: R -
Q . :
B -
H R- NH 2 B -
¤ H : 必 -
h
…
Least Stable
↓ must stable
~
45 -
50 35 -
40 1的 -
18 -
b0 -
3 prka
, Reagent for depronating an alcohol
There a re 2 ways to depronate an alcohol , forming an alkoxide ion
2) A
strong base can be used to depronate the alcohol .
A commonly base is Natt ,
because hydride (HO) depronate
the alcohol to generate hydrogen gas :
~ㄱ
NP- + H
Ethanol sodiumtlydale sodium ethoxide Hydrogen gas
b Alternatively , an alwhol can be depronated upon
treatment with Li , Na or K .
These metals react withthe alcohol to liberate
hydrogen gas, producing alkoxide ion
¤'
… →
〜 ¤ N +
芝
-
Converted alcohol upon treatment Hgot
e) into its
corresponding with acid , Such a s
ㅐ
~ θ 0
θ . .
.
거 내
R -
℃ : _ R- -
H
An alkoxide Amalcohol
)
↳ Hzst can be prepared by diluting a
strong acid , such an Ha or HaSUp ,
in water , although there a re other ways to prepare even
milder aqueous acidic condition
Factors
affecting the acidity of alcohols and phenols
significant the
1 Resonance one of the most factors affecting acidity of alcohols and
phenols is resonance
-
매 애
Cyclohexanol phendl
(pka = (2) (pka = (s)
When pheno depronated , the conj bane is stabilized
is .
by resonance
θ
ㅣ
_
出感感速
:O: : 0:
=> This resonance stabilized anion in called
ㄴ
→→ phenolate/phenoxide
↳ Phenol does Not need to depronated with a
very strong
bare like sodium hydride) It can be depronated
by
INn
@ hydroxide
※ :0
⑤⑧ →
⑤ + + h 20
pKa = 15 f .
BKa = 10 0
.
立
飛
, 2
, Induction :
el
〜
os Non => Trichloroethanol is 4 orders of magnitude more acidic than
^
a
디
Ethano I Trichloroethand ethanol ,
because the cors.bane of trichloroethanol is stabilited
(pka = 16 .. 0) (pka = 12 . 2) by the electron-withdrawing effects of the nearby chloride
atoms
The effect
3) solvation effects :
of alkyl branching .
√
-H rot => This difference in
acidity is best explained by a steric effect
…
ethanol tert-Butanol o The ethoxide ion is not
sterically hidered and is therefore more
CpKa = 16 . 0) (pka = 18 .
0)
Solvation Effects
.
3 : To explore the effect of alky/ branching , comparethe acidity of ethanol and tert-butand
〜 √
therefore
o n Λ ol => The ethoxide
sterically hindered and
새
ion i s not is
-
…
Ethand tert-butaho7 more solvated (stabilized) by the solvent , while tert-butanol
CpKa = 16 . 0) ( pKa = 18 03 .
is
sterically hindered and less solvated
Preparation of alcohols via substitution/addition
* Substitution Reaction
、
R -X >
- >
R -
OH
Primcry :
~
i SN2
> XoU
+ Naoh- +
Nad
Tertiary :
→ si ·
~
a - e 〜
t 4 ' ^ + HC
^
애
CMark-addition)
DiluteH2 S04
Additio Reactions Acid-eatalyzed hydration
>
ㅅ
H 20 매
へ 1> Hg(OAC) 2 ,
oxymearation -demecration
ㅣ
>
Λ
2,
NaBHy CMark-addition)
1) BH3 , THF 0m Hydroboration - oxidation
~
7
2 H202 , Naot CAnti-mark)
