Chemistry Reference
In-Depth Information
Table 5.2
Group Molar Attraction Constants
[4]
Group
Molar attraction
F
i
Group
Molar attraction
F
i
(cal/cc)
1/2
/mol
(cal/cc)
1/2
mol
a
CH3
148.3
a
H acidic dimer
50.47
2
a
CH2
a
131.5
OH aromatic
170.99
CH
a
85.99
NH
2
226.56
.
a
C
a
with no H
32.03
NH
180.03
.
CH2
Q
olefin
126.54
N
a
61.08
.
a
CH
Q
olefin
121.53
C
R
N
354.56
CH
Q
olefin
84.51
NCO
358.66
.
a
CH
Q
aromatic
117.12
a
S
a
209.42
a
C
Q
aromatic
98.12
Cl
2
342.67
a
O
a
(ether, acetal)
114.98
Cl primary
205.06
a
O
a
(epoxide)
176.20
Cl secondary
208.27
a
COO
a
326.58
Cl aromatic
161.0
.
CQO
262.96
Br
257.88
aCHO
292.64
Br aromatic
205.60
(CO)
2
O
567.29
aOHa
225.84
F
41.33
Structure feature
Structure feature
Conjugation
23.26
6-Membered ring
23.44
2
Cis
7.13
Ortho substitution
9.69
2
Trans
13.50
Meta substitution
6.6
2
4-Membered ring
77.76
Para substitution
40.33
5-Membered ring
20.99
the molar attraction constants. A modified version of a compilation
[4]
of molar
attraction constants is reproduced in
Table 5.2
.
Examples of the use of the tabulated molar constants are given in
Fig. 5.1
.
Such group contribution methods are often used in engineering estimations of
other thermodynamic properties.
The solubility parameter of random copolymers
δ
c
may be calculated from
X
δ
c
5
δ
i
w
i
(5-14)
where
δ
i
is the solubility parameter of the homopolymer that corresponds to
monomer i in the copolymer and w
i
is the weight fraction of repeating unit i in
the copolymer
[5]
. Alternating copolymers can be treated by taking the copolymer
repeating unit as that of a homopolymer (see
Fig. 5.1c
for example). No satisfac-
tory method exists for assigning values to block or graft copolymers.
Mixtures of solvents are often used, especially in formulating surface coatings.
It is not unusual to find that a mixture of two nonsolvents will be a solvent for a
