This document analyzes which is a better predictor of boiling point for alcohol isomers - molecular weight or number of carbon chains. Regression analysis was performed using molecular weight and carbon chains as independent variables to predict boiling point (dependent variable) for alcohols with 5-12 carbons. The regression equations were then used to predict boiling points for structural isomers of butanol, pentanol, and hexanol and percent errors calculated. Molecular weight predictions had 14-20% errors while carbon chain predictions were slightly better with 14-15% errors.

1. Which model is a better predictor, using molecular weight or number of carbon chain
2 or more independent variable (predictor)
Is boiling point associated with molecular weight and carbon chains.
Molecular weight or number of carbon chains – independent variables (predictor)
Boiling point of alcohol isomers – dependent variable (outcome)
Using Regression and Anova for analysis
Independent variable
Dependent variable
Is molecular weight or number carbon chains a good predictor
Independent variable Dependent
variable
Data for b/p from CRC Handbook. Click here data
IA secondary data based – Regression analysis for boiling point estimation for alcohol isomers, (butanol, pentanol, hexanol)
B/point = x1 (molecular weight) + intercept
B/point = x1 (number of carbons) + intercept or
Research Question
Use 5 -12 carbon chains for regression model
Use regression to predict b/p for isomers of alcohol, butanol, pentanol, hexanol.
Find the % error using expt values with predicted values.
Using molecular weight, 2nd order as predictor for b/p.
Using carbon chain 2nd order as predictor for b/p.
MF
Number
carbon
Molecular
weight b/p
CH3OH 1 32.04 64.7
C2H5OH 2 46.09 78
C3H7OH 3 60.09 97
C4H9OH 4 74.12 117.7
C5H11OH 5 88.15 138
C6H13OH 6 102.16 157
C7H15OH 7 116.88 175

2. Isomerism
Molecules with same molecular formula but diff arrangement of atom
Two types of Isomerism
Positional Chain Isomer Functional Gp Isomer
C – C – C – C – OH
C4H10O1
Structural Isomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
Diff hydrocarbon chain skeleton
• Same molecular formula
• Same structural formula
• Diff spatial arrangement of atom
Stereoisomerism
Hydrocarbon Chain Isomer
Diff functional gp position Diff functional gp
C – C – C – OH
‫׀‬
CH3
C – C – C –C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – C
‫׀‬
OH
C – C – C – O – C
Optical Isomer
Geometric Isomer
Isomer Physical
property
Chemical
property
Structural isomer
- Hydrocarbon chain
- Functional gp position
- Functional gp
Different
Different
Different
Similar
Similar
Different
Geometrical isomer Different Similar
Optical isomer Similar Similar
Structural formula – arrangement atoms in molecule (2/3D)
H H
‫׀‬ ‫׀‬
H - C – C – H
‫׀‬ ‫׀‬
H H
CH3CH3
ethane
Display full SF Condensed SF Ball/stick model Spacefilling
Click here chemical search.
Data source for b/p
Data PubChem. Click here
Data PubChem. Click here
Data Handbook. Click here data

3. Diff functional
gp position
C4H9OH
Structural Isomerism
• Same molecular formula
• Diff structural formula
• Diff arrangement of atom
Diff hydrocarbon
chain skeleton
Diff functional
gp position
Diff functional gp
CH3-CH2-CH2-CH3
‫׀‬
OH
Butan–1-ol
CH3-CH-CH2-OH
‫׀‬
CH3
2-Methylpropan-1-ol
CH3
‫׀‬
CH3-C-OH
‫׀‬
CH3
CH3-CH2-CH-CH3
‫׀‬
OH
2-Methylpropan-2-ol Butan-2-ol
CH3-CH2-CH2-O-CH3
Methoxypropane
CH3-CH2-O-CH2-CH3
Ethoxyethane
7 structural isomers
CH3-CH-O-CH3
‫׀‬
CH3
CH3-CH2-CH2=CH2
C4H8
CH3-CH=CH-CH3
CH3-C=CH2
‫׀‬
CH3
CH2 – CH2
‫׀‬ ‫׀‬
CH2 - CH2
C4H9Br
CH3-CH2-CH2-CH2
‫׀‬
Br
CH3-CH2-CH-CH3
‫׀‬
Br
CH3
‫׀‬
CH3-C-Br
‫׀‬
CH3
CH3- CH-CH2
‫׀‬ ‫׀‬
CH3 Br
C6H14
CH3-CH2-CH2-CH2-CH2-CH3 CH3-CH-CH2-CH2-CH3
‫׀‬
CH3
CH3-CH2-CH-CH2-CH3
‫׀‬
CH3
CH3
‫׀‬
CH3-C-CH2-CH3
‫׀‬
CH3
CH3- CH- CH-CH3
‫׀‬ ‫׀‬
CH3 CH3
Diff hydrocarbon
chain skeleton
Diff functional
gp position
Diff functional
gp
Diff hydrocarbon
chain skeleton
4 structural isomers 4 structural isomers
5 structural isomers
Diff hydrocarbon
chain skeleton

4. Homologous Series
Class Functional Suffix Example Formula
Alcohol Hydroxyl - ol methanol CnH2n+1OH
• member differ by CH2 gp
• same functional group
• similar chemical properties
• chemical formula CnH2n+1OH
• end with ol
Number
carbon
IUPAC
name
Structure formula b/p
1 Methanol CH3OH 64.7
2 Ethanol CH3CH2OH 78
3 Propanol CH3CH2CH2OH 97
4 Butanol CH3(CH2)2CH2OH 117.7
5 Pentanol CH3(CH2)3CH2OH 138
methanol ethanol propanol butanol
H
‫׀‬
H - C – OH
‫׀‬
H
H H
‫׀‬ ‫׀‬
H - C – C – OH
‫׀‬ ‫׀‬
H H
H H H
‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – OH
‫׀‬ ‫׀‬ ‫׀‬
H H H
H H H H
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H - C – C – C – C – OH
‫׀‬ ‫׀‬ ‫׀‬ ‫׀‬
H H H H
Hydrocarbon skeleton Functional gp
b/p
increase ↑
Physical properties
• Increase RMM / molecular size
•RMM increase ↑ - Van Der Waals forces stronger ↑
↓
boiling point increases ↑
(Increasing polarisability ↑)
London dispersion forces/temporary dipole ↑
Number
carbon
Molecular
weight b/p
1 32.04 64.7
2 46.09 78
3 60.09 97
4 74.12 117.7
5 88.15 138
6 102.16 157
7 116.88 175
8 130.23 195
9 144.26 214
10 158.28 230
11 172.31 243
12 186.34 260
14 214.39 289
15 228.41 299
17 256.5 308
19 284.5 345
Boiling point for diff alcohol
boiling point increase with increase carbon atoms

5. MW 2nd order as predictor for b/p for alcohol CC 2nd order as predictor for b/p for alcohol
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for structural isomers of alcohol (butanol, pentanol, hexanol)
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.
y = -0.0021x2 + 1.8371x - 8.0951
R² = 0.999
0
100
200
300
0 50 100 150 200
b/p
molecular weight
molecular weight vs b/p
y = -0.4405x2 + 24.964x + 23.44
R² = 0.9992
0
100
200
300
0 2 4 6 8 10 12 14
b/p
carbon chain
carbon chain vs b/p
Can both model be used to predict b/p for
isomer of alcohol (Butanol, pentanol hexanol)
Structural Isomers
4 carbons
b/p
predict
MW
(% error)
predict
CC
(% error)
1- butanol 117.7
2- butanol 99
2- methyl propan-1-ol 108
2-methyl propan-2-ol 82
Min b/p 102
Max b/p 138
Mean b/p 102
Structural Isomers
5 carbons
b/p
predict
MW
(% error)
predict CC
(% error)
1- pentanol 138
2- pentanol 119
3 – pentanol 116
2-methylbutan-1-ol 129
3-methylbutan-1-ol 131
2-methylbutan-2-ol 102
3-methylbutan-2-ol 112
2,2-dimethylpropanol 113
Min b/p 102
Max b/p 138
Mean b/p 120
Structural Isomers
6 carbons
b/p predict MW
(% error)
predict CC
(% error)
1- hexanol 157
2- hexanol 140
3 – hexanol 135
2,3 –dimethylbutan-2-ol 118
3,3 –dimethylbutan-1-ol 136
2-methylpentan-1-ol 149
3-methylpentan-1-ol 153
4-methylpentan-1-ol 151
2-methylpentan-2-ol 121
3-methylpentan-2-ol 134
4-methylpentan-2-ol 131
2-methylpentan-3-ol 126
3-methylpentan-3-ol 122
Min b/p 118
Max b/p 157
Mean b/p 136

6. Predicted b/p for carbon 4 – MW of 74.12
2nd order fit, y = -0.0021x2 + 1.837x – 8.095
b/p= -0.0021(74.12)2 + 1.837(74.12) – 8.095 = 116
% error =
(𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆 −𝑷𝒓𝒆𝒅𝒊𝒄𝒕𝒆𝒅 𝒗𝒂𝒍𝒖𝒆)
𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆
x 100%
% error =
(𝟏𝟎𝟐−𝟏𝟏𝟔)
𝟏𝟎𝟐
x 100% = 14%
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for structural isomers of butanol (4 carbons)
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.
Structural Isomers
4 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
1- butanol 117.7
2- butanol 99
2- methyl propan-1-ol 108
2-methyl propan-2-ol 82
Min b/p 102
Max b/p 138
Mean b/p 102 116 (14%) 116 (14%)
Predicted b/p for carbon 4
2nd order fit, y = -0.44x2 + 24.96x + 23.44
b/p= -0.44(4)2 + 24.96(4) + 23.44 = 116
All isomers 4 carbon alcohol have same MW – 74.12

7. Predicted b/p for carbon 5 – MW of 88.15
2nd order fit, y = -0.0021x2 + 1.837x – 8.095
b/p= -0.0021(88.15)2 + 1.837(88.15) – 8.095 = 145
% error =
(𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆 −𝑷𝒓𝒆𝒅𝒊𝒄𝒕𝒆𝒅 𝒗𝒂𝒍𝒖𝒆)
𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆
x 100%
% error =
(𝟏𝟐𝟎−𝟏𝟒𝟓)
𝟏𝟐𝟎
x 100% = 20%
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for structural isomers of pentanol (5 carbons)
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.
Structural Isomers
5 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
1- pentanol 138
2- pentanol 119
3 – pentanol 116
2-methylbutan-1-ol 129
3-methylbutan-1-ol 131
2-methylbutan-2-ol 102
3-methylbutan-2-ol 112
2,2-dimethylpropanol 113
Min b/p 102
Max b/p 138
Mean b/p 120 145 (20%) 137 (14%)
Predicted b/p for carbon 5
2nd order fit, y = -0.44x2 + 24.96x + 23.44
b/p= -0.44(5)2 + 24.96(5) + 23.44 = 137
All isomers 5 carbon alcohol have same MW – 88.15

8. Predicted b/p for carbon 6 – MW of 102.16
2nd order fit, y = -0.0021x2 + 1.837x – 8.095
b/p= -0.0021(102.16)2 + 1.837(102.16) – 8.095 = 157
% error =
(𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆 −𝑷𝒓𝒆𝒅𝒊𝒄𝒕𝒆𝒅 𝒗𝒂𝒍𝒖𝒆)
𝑬𝒙𝒑𝒕 𝒗𝒂𝒍𝒖𝒆
x 100%
% error =
(𝟏𝟑𝟔−𝟏𝟓𝟕)
𝟏𝟓𝟕
x 100% = 15%
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for structural isomers of hexanol (6 carbons)
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.
Structural Isomers
6 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
1- hexanol 157
2- hexanol 140
3 – hexanol 135
2,3 –dimethylbutan-2-ol 118
3,3 –dimethylbutan-1-ol 136
2-methylpentan-1-ol 149
3-methylpentan-1-ol 153
4-methylpentan-1-ol 151
2-methylpentan-2-ol 121
3-methylpentan-2-ol 134
4-methylpentan-2-ol 131
2-methylpentan-3-ol 126
3-methylpentan-3-ol 122
Min b/p 118
Max b/p 157
Mean b/p 136 157 (15%) 157 (15%)
Predicted b/p for carbon 6
2nd order fit, y = -0.44x2 + 24.96x + 23.44
b/p= -0.44(6)2 + 24.96(6) + 23.44 = 157
All isomers 6 carbons alcohol have same MW – 102.16

9. carbon chain 2nd order model
molecular weight 2nd order model
% error 2nd order for both model are relatively the same.
2nd order fit – % error changes from 14% to 14% to 15% as
carbon chain changes from 4 to 5 to 6.
Both model produced about 14 -15% error.
y = -0.4405x2 + 24.964x + 23.44
R² = 0.9992
0
50
100
150
200
250
300
0 2 4 6 8 10 12 14
b/p
carbon chain
carbon chain vs b/p
y = -0.0021x2 + 1.8371x - 8.0951
R² = 0.999
0
50
100
150
200
250
300
0 50 100 150 200
b/p
molecular weight
molecular weight vs b/p
Structural Isomers
4 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
Mean b/p 102 116 (14%) 116 (14%)
Structural Isomers
5 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
Mean b/p 120 145 (20%) 137 (14%)
Structural Isomers
6 carbons
b/p
predict using
MW
(% error)
predict using
CC
(% error)
Mean b/p 136 157 (15%) 157 (15%)
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for structural isomers of alcohol (butanol, pentanol, hexanol)
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.

10. carbon chain 2nd order model
molecular weight 2nd order model
% error 2nd order for both model are relatively the same.
% error using CC appears to be smaller
compared to MW model.
% error small 2-4% for non aromatic cyclic OH.
Both model produced about 11 -19% error for aromatic OH.
y = -0.4405x2 + 24.964x + 23.44
R² = 0.9992
0
100
200
300
0 2 4 6 8 10 12 14
b/p
carbon chain
carbon chain vs b/p
y = -0.0021x2 + 1.8371x - 8.0951
R² = 0.999
0
100
200
300
0 50 100 150 200
b/p
molecular weight
molecular weight vs b/p Molecules
with OH
Molecular
weight
Number carbon b/p predict
using MW
(% error)
predict
using CC
(% error)
phenol 94.11 6 181.7 146 (19%) 157 (13%)
3 methylphenol 108.14 7 203 166 (18%) 177 (13%)
2 phenylethanol 122.16 8 219 185 (16%) 195 (11%)
Cyclohexanol 100.15 6 161 154 (4%) 157 (2%)
Research Question
Use 5- 12 carbon chains for regression model
Use regression to predict b/p for aromatic molecules with OH gps.
Using molecular weight (MW) 2nd order as predictor for b/p.
Using carbon chain (CC) 2nd order as predictor for b/p.
Phenol 3 methylphenol 2 phenylethanol cyclohexanol