SOLVENTS

Solvent is a substance, usually a liquid, that acts as a dissolving agent or that is capable of dissolving another substance. In solutions of solids or gases in a liquid, the liquid is the solvent. In all other homogeneous mixtures (i.e., liquids, solids, or gases dissolved in liquids; solids in solids; and gases in gases), solvent is the component of the greatest amount. The minor proportion substances are called solutes. The solvent offers several functions during a chemical reaction. It solves not only the substance that reacts with another one to produce a new set of substances (reactant) but also the compound that supplies the molecule, ion, or free radical, which is considered as the attacking species in a chemical reaction (reagent). The solvent is conductive to collisions between the reactants and reagents to transform the reactants to new products. The solvent also takes roll of temperature control, either to provide the energy of the colliding particles for speedy reaction and to absorb heat in exothermic reaction. The appropriate solvent should be selected based on the inactivity in the reaction conditions, dissolving the reagents as well as reactants, appropriate boiling point and easy removal at the end of the reaction.

Polarity

The most common solvent is water. Other common solvents which dissolve substances that are insoluble (or nearly insoluble) in water are acetone, alcohol, formic acid, acetic acid, formamide. BTX, carbon disulfide, diemthyl sulfoxide, carbon tetrachloride, chloroform, ether, tetrahydrofuran, furfural, hexane and turpentine. They may be classified as polar and non-polar. Polar solvents, like water, have molecules whose electric charges are unequally distributed, leaving one end of each molecule more positive than the other. Usually polar solvent has O-H bond of which water (HOH), (CH3OH) and acetic acid (CH3COOH) are examples. Propanol, butanol, formic acid, formamide are polar solvents. Dipolar solvents which contain a C-O double bond without O-H bond are acetone [(CH3)2C=O], ethyl acetate (CH3COOCH2CH3), methyl ethyl ketone, acetonitrile, N,N-dimethylformamide and diemthyl sulfoxide. Nonpolar solvents, like carbon tetrachloride (CCl4), benzene (C6H6), and diethyl ether ( CH3CH2OCH2CH3), have molecules whose electric charges are equally distributed and are not miscible with water. Hexane, tetrahydrofuran and methylene chloride are non-polar solvents. Polar solvents are hydrophilic but non-polar solvents are lipophilic. Polar reactants will dissolve in polar solvents. Non-polar solvents dissolve non-polar compounds best. Oil and water don't mix but separate into two layers. There are three measures of the polarity as "dipole moment", "dielectric constant" and "miscibility with water". Though low dipole moments and small dielectric constants indicates non-polar solvents, sharp boundaries between polar and non-polar solvents are not available. The polarity reflects the balance between a polar component (OH) and a non-polar hydrocarbon component, existing in the same molecule. If hydrocarbon character increases relatively, the polarity decreases. On an operational basis, solvents that are miscible with water are polar.

Polar Protic and Dipolar Aprotic

Protic refers to a hydrogen atom attached to an electronegative atom. Protic solvents can donate an H+ (proton) since they contain dissociable H+, such as hydrogen attached to oxygen as in a hydroxyl group, nitrogen as in a amine group. Examples are water, methanol, ethanol, formic acid, hydrogen fluoride and ammonia. Aprotic solvents don't has O-H bond but a C=O bond typically. Examples are acetone [(CH3)2C=O] and ethyl acetate (CH3COOCH2CH3). Polar protic solvents are useful in SN1 reaction, while polar aprotic solvents are SN2 reaction.

Polarity Order

Polarity

Group

Formula

Polar

Water

H-OH

↑

Carboxylic Acids

R-COOH

↑

Amides

R-CONH2

↑

Alcohols

R-OH

↑

Amines

R-NH2

↑

Ketones (Aldehydes)

R-CO-R'

↑

Esters

R-COOR'

↑

Alkyl Halides

R-X

↑

Ethers

R-O-R'

↑

Aromatics

Ar-H

Non-polar

Alkanes

R-H

Physical Properties of Common Solvents 

Solvent

CAS RN

 Formula M.W. Boiling Point (°C) Melting Point (°C) Density Solubility in water (g/100g) Dielectric Constant Flash Point (°C)
Acetic Acid 64-19-7 C2H4O2 60.05 118 16.6 1.049 Miscible 6.15 39

Acetic Anhydride

 108-24-7 C4H6O3 102.09

138-140

 -73.11.0812

-

54
Acetone 67-64-1 C3H6O 58.08 56.2 -94.3 0.786 Miscible 20.7(25) -18
Acetonitrile 75-05-8 C2H3N 41.05 81.6 -46 0.786 Miscible 37.5 6
Ammonia solution 7664-41-7 H3N 17.03

-

-

-

-

 22.4

-
Benzene 71-43-2 C6H6 78.11 80.1 5.5 0.879 0.18 2.28 -11

Benzonitrile

 100-47-0 C7H5N 103.12

191

 -13 1.01 Insoluble

-

 71
1-Butanol 71-36-3 C4H10O 74.12 117.6 -89.5 0.81 6.3 17.8 35
2-Butanol 78-92-2 C4H10O 74.12 98 -115 0.808 15 15.8(25) 26

Butyl Acetate

 123-86-4 C6H12O2 116.16

124-126

 -106 0.882 0.68

-

22
tert-Butyl Alcohol 75-65-0 C4H10O 74.12 82.2 25.5 0.786 Miscible 12.5 11
tert-Butyl Methyl Ether 1634-04-4 C5H12O 88.15 55.2 -109 0.741 5.1

-

-28

Carbon Disulfide

 75-15-0 CS2 76.13

46

 -110 1.2632 0.1185

-

 -30
Carbon Tetrachloride 56-23-5 CCl4 153.82 76.7 -22.4 1.594 0.08 2.24 -
Chlorobenzene 108-90-7 C6H5Cl 112.56 131.7 -45.6 1.1066 0.05 2.71 29

1-Chlorobutane

 109-69-3 C4H9Cl 92.57

77-78

 -123.1 0.886 0.07

-

 -6
Chloroform 67-66-3 CHCl3 119.38 61.7 -63.7 1.498 0.795 4.81

-

Cyclohexane 110-82-7 C6H12 84.16 80.7 6.6 0.779 <0.1 2.02 -20
Deuterium oxide 7789-20-0 D2O 20.03 101.3 4 1.107 Miscible

-

-

1,2-Dichlorobenzene

 95-50-1 C6H4Cl2 147.00

180

 -15 1.306 Insoluble

9.93(25)

67
1,2-Dichloroethane 107-06-2 C2H4Cl2 98.96 83.5 -35.3 1.245 0.861 10.42 13
Diethyl Amine 109-89-7 C4H11N 73.14 55.5 -50 0.7074 Miscible 3.6 -39
Diethyl Ether 60-29-7 C4H10O 74.12 34.6 -116.3 0.713 7.5 4.34 -45
Diethyl Ketone 96-22-0 C5H10O 86.13

102

 -39 0.814 4.70

-

 13
Diethylene Glycol Dimethyl Ether 111-96-6 C6H14O3 134.17 162 -68 0.943 Miscible 7.23 67
Diethylene Glycol 111-46-6 C4H10O3 106.12 245 -10 1.118 10 31.7 143
Dimethyl Sulfoxide 67-68-5 C2H6OS 78.13 189 18.4 1.092 25.3 47 95

N,N-Dimethylacetamide

 127-19-5 C4H9NO 87.12

166

-20

0.937Miscible

37.80

66
Dimethylether 115-10-6 C2H6O 46.07 -22 -138.5

-

-

-

-41
N,N-Dimethylformamide 68-12-2 C3H7NO 73.09 153 -61 0.944 Miscible 36.7 58
1,4-Dioxane 123-91-1 C4H8O2 88.11 101.1 11.8 1.033 Miscible 2.21(25) 12
Ethanol 64-17-5 C2H6O 46.07 78.5 -114.1 0.789 Miscible 24.6 13

2-Ethoxyethyl Ether

 112-36-7 C8H18O3 162.23

180-190

 -44 0.909 ≥10

-

82
Ethyl Acetate 141-78-6 C4H8O2 88.11 77 -83.6 0.895 8.7 6(25) -4

Ethylene Glycol Dimethyl Ether

 110-71-4 C4H10O2 90.12 85 -58 0.868 Miscible 7.2 -6
Ethylene Glycol 107-21-1 C2H6O2 62.07 195 -13 1.115 Miscible 37.7 111
Formic Acid 64-18-6 CH2O2 46.03 100 8.3 1.21 Miscible 58.5

 
Glycerin 56-81-5 C3H8O3 92.09 290 17.8 1.261 Miscible 42.5 160
heptane 142-82-5 C7H16 100.20 98 -90.6 0.684 0.01 1.92 -4
Hexamethylphosphor amide 680-31-9 C6H18N3OP 179.20 232.5 7.2 1.03 Miscible 31.3 105
Hexamethylphosphorous triamide 1608-26-0 C6H18N3P 163.20 150 -44 0.898 Miscible

-

26
Hexane 110-54-3 C6H14 86.18 69 -95 0.659 0.014 1.89 -22

Isoamyl alcohol

 123-51-3 C5H12O 88.15

130

 -117 0.809 54

-

 43

Isobutyl alcohol

 78-83-1 78-83-1 74.12

108

 -108 0.802 9.5

15.8(25)

 28
Isopropanol 67-63-0 C3H8O 88.15 82.4 -88.5 0.785 Miscible 18.3(25) 12
Methanol 67-56-1 CH4O 32.04 64.6 -98 0.791 Miscible 32.6(25) 12

2-Methoxyethanol

 109-86-4 C3H8O2 76.10

124-125

 -85.10.965Miscible

16.90

38

2-Methoxyethyl Acetate

 110-49-6 C5H10O3 118.13

145

 -651.009Miscible

-

44

Methyl Ethyl Ketone

 78-93-3 C4H8O 72.11 79.6 -86.3 0.805 25.6 18.5 -7

Methyl Isobutyl Ketone

 108-10-1 C6H12O 100.16

117-118

 -800.79781.9

-

14
1-Methyl-2-pyrrolidinone 872-50-4 CH5H9NO 99.13 202 -24 1.033 10 32 91
Methylene Chloride 75-09-2 CH2Cl2 84.93 39.8 -96.7 1.326 1.32 9.08 1.6
Nitromethane 75-52-5 CH3NO2 61.04 101.2 -29 1.382 9.50 35.9 35
1-Octanol 111-87-5 C8H18O 130.23

196

 -15 0.826 Insoluble

-

 81
Pentane 109-66-0 C5H12 72.15 36.1 -129.7 0.626 0.04 1.84 -49
Petroleum ether 8032-32-4

-

-

30-60 -40 0.656

-

-

-30
Propanoic acid 79-09-4 C3H6O2 74.08 141 -21.5 0.993 37 3.4 51
1-Propanol 71-23-8 C3H8O 88.15 97 -126 0.803 Miscible 20.1(25) 15

Propylene carbonate

 108-32-7 C4H6O3 102.09

240

 -55 1.21 Moderately Soluble

-

 132
Pyridine 110-86-1 C5H5N 79.10 115.2 -41.6 0.982 Miscible 12.3(25) 17

Tetrachloroethylene

 127-18-4 C2Cl4 165.83

121

 -22 1.623 0.015

-

-
Tetrahydrofuran 109-99-9 C4H8O 72.11 66 -108.4 0.886 30 7.6 -21
Toluene 108-88-3 C7H8 92.14 110.6 -93 0.867 0.05 2.38(25) 4

1,1,2-Trichlorotrifluoroethane

 76-13-1 C2Cl3F3 187.38

47-48

 -36 1.575 0.02

-

-
Triethyl amine 121-44-8 C6H15N 101.19 88.9 -114.7 0.728 0.02 2.4 -11
2,2,2-Trifluoroethanol 75-89-8 C2H3F3O 100.04 74.1 -45 1.393

-

 26.5

29
Water 7732-18-5 H2O 18.02 100.00 0.00 0.998

-

78.54 -
m-Xylene 108-38-3 C8H10 106.17 139.1 -47.8 0.868 Insoluble 2.37 27
o-Xylene 95-47-6 C8H10 106.17 144 -25.2 0.897 Insoluble 2.57 32
p-Xylene 106-42-3 C8H10 106.17 138.4 13.3 0.861 Insoluble 2.27 27