0
0
--0-6: ----XX-
molecular
weight
0-6:
X -
O-H
0
group
If X = electron withdrawing group
This stabilizes anion.
Thus making acid more acidic
group
If X = electron donating group
This destabilizes anion.
Thus making acid less acidic
boiling
point
solubility
in H 2O
CH3-CH2-CH2-CH2-CH3
72
36°C
no
CH 3-CH 2-O-CH 2-CH 3
74
35
yes
CH 3-CH 2-CH 2 -CH 2 ·OH
74
//0
~
yes
72
76
yes
72
80
yes
74
B
CH 3-CH 2-CH 2 -C\
H
pK a
0
6:°
0
II
CH 3-CH 2 -C\
CH 3
4.2
O-H
0
11
-C\
CH 3-CH 2 -C\
OH
OH
/0
3.8
O
2 N - o C ' \l
-.--O-H
I miscible
0
//
CH 3 -CH 2 -CH 2 - C\
C\
OH
OH
/0
CH 3
-Q-l
~
\
-
miscible
4.3
0
O-H
II
still
soluble
-C\
CH T CH T CH 2-CH 2-C\
OH
OH
pK a Values of Some Organic Acids
stronger
acid
acid
weaker
weaker
acid
sulfuric acid
H-OS0 3 H
trichloroacetic
acid
acid
H-OOCCCI 3
dichloroacetic
acid
H-OOCCHCI 2
1.5
chloroacetic
acid
H-OOCCH 2 CI
2.9
3-chloropropionic acid
H-OOCCH 2 CH 2 CI
4.0
acetic acid
H-OOCCH 3
4.7
4.7
phenol
H-OPh
10
10
-9
- -9
0.6
0.6
O-----H-O
II
R-C
\
\
~C-R
O-H----O
'/
carboxylic acids exist
as hydrogen bonded
dimers
th~s ha~e high boiling
pOints since effective
m?'ecu'ar weight
IS Increased
O-----H-O
II
\
R-C
\
water
H-OH
15.7
H"
ethanol
H-OCH 2 CH 3
"O-H,
"
,
\
16
/0
H
see McMurry section 10.3
" ,,/'
0
~
H
H
solubility of
carboxylic acids
in water due to
hydrogen bonds
I