Toluene is an aromatic hydrocarbon with the chemical formula C6H5CH3, frequently abbreviated as PhCH3, The Ph in the abbreviation stands for the phenyl group.
Toluene is a derivative of benzene. It is a colorless, water-insoluble liquid with the 
associated with paint thinners.
It consists of a methyl group (CH3) connected to a phenyl group by a single bond.
As such, its IUPAC name is methylbenzene. Toluene is predominantly used as an industrial fuel and a solvent. The toluene intermolecular forces are the London dispersion forces.
Toluene Intermolecular Forces
We can consider the arrangement of toluene. It is a covalent compound. Subsequently, it forms electron pairs as well as a hydrocarbon compound because it only contains carbon and hydrogen atoms.
Technically, this molecule contains polar “C-H” bonds because carbon is slightly more electronegative than hydrogen, but by definition. However, we generally describe hydrocarbon compounds as being relatively nonpolar.
If we bring two non-polar toluene molecules together, then they will primarily interact using London-dispersion forces; the interaction is based on instantaneous dipoles being formed on one toluene molecule due to a temporary redistribution in the valence electrons.
The toluene intermolecular forces are the London dispersion forces. This instantaneous dipole induces an instantaneous dipole in another toluene molecule and so on.
Strongest Toluene Intermolecular Forces
The strongest toluene intermolecular forces are its London dispersion forces.
London dispersion forces are a type of intermolecular force acting between atoms and molecules that are normally electrically symmetric; that is, the electrons are symmetrically distributed concerning the nucleus.
While they’re the weakest of the intermolecular forces, they’re still significant because toluene is a non-polar molecule. These forces affect the boiling point of toluene, which is around 110 degrees Celsius.
They also affect the melting point of toluene, which is just below -95 degrees Celsius. These forces also make toluene insoluble in water but soluble in organic solvents.
What Are Intermolecular Forces?
Intermolecular forces are the attractive and repulsive forces that arise between the molecules of a substance.
These forces mediate the interactions between individual molecules of a substance. They are what make molecules stick together and form liquids, solids and other phases of matter.
Intermolecular forces are responsible for most of the physical and chemical properties of matter. The physical properties of matter include its melting and boiling points.
Forces also exist between the molecules themselves and these are collectively referred to as intermolecular forces. Intermolecular forces are mainly responsible for the physical characteristics of the substance.
Intermolecular forces are responsible for the condensed states of matter. The particles making up solids and liquids are held together by intermolecular forces and these forces affect a number of the physical properties of matter in these two states. Intermolecular forces also affect a number of the chemical properties of matter.
Types of Intermolecular Forces
An intermolecular force is an attractive force that arises between the positive components (or protons) of one molecule and the negative components (or electrons) of another molecule.
Different physical and chemical properties of a substance are dependent on this force. The boiling point of a substance is proportional to the strength of its intermolecular forces; the stronger the intermolecular forces, the higher the boiling point. The intermolecular forces depend on the following interactions:
1. Dipole-Dipole Interactions:
Dipole-dipole interactions are attractive forces among polar molecules. Polar molecules have permanent dipoles that are formed due to differences in the electronegativities of the atoms that are associated with a covalent bond.
The partially positive portion of one molecule is attracted to the partially negative portion of another molecule.
Example: Dipole-dipole interactions occur in HCl molecules. Chlorine is comparatively more electronegative than hydrogen and it, therefore, acquires a partial negative charge (whereas hydrogen acquires a partial positive charge). The dipole-dipole interaction then takes place between the HCl molecules.
2. Ion-Dipole Interactions:
These interactions are similar to dipole-dipole interactions except for the fact that they arise between ions and polar molecules.
Example: When NaCl is mixed with water in a beaker, the polar H2O molecules are attracted to the sodium and chloride ions in the beaker.
The strength of this interaction depends on:
- The magnitude of the dipole moment
- Size of the polar molecule
- The size and charge of an ion
3. Ion-induced dipole interactions:
In this type of interaction, a non-polar molecule is polarised by an ion placed near it. The non-polar molecules, upon obtaining a charge, behave as induced dipoles.
This interaction between an ion and an induced dipole is known as ion-induced dipole interaction.
4.-induced dipole interaction:
These interactions are similar to ion-induced dipole interactions. However, the differentiating factor is that non-polar molecules are transformed into induced dipoles due to the presence of a polar molecule nearby.
5. Dispersion Forces or London Forces:
It operates for a short distance and it is the weakest force. This kind of force arises due to the movement of electrons, thus creating temporary positive and negative charged regions.
History of Toluene
During the year 1837, a compound was isolated through the distillation of pine oil by the Polish chemist Filip Walter. Filip Walter named it retinnaphte. In the year 1841, a French chemist with the name Henri Etienne Sainte-Claire Deville isolated a hydrocarbon from the balsam of Tolu.
The compound was an aromatic extract from the tropical Colombian tree, Myroxylon balsamum. He recognized that it was comparable to Walter’s retinnaphte and benzene. Therefore, he called the new hydrocarbon benzoene.
In 1843, Jöns Jacob Berzelius proposed the name toluin for the same compound. The French chemist Auguste Cahors separated a compound from a distillate of wood, a hydrocarbon that he acknowledged as similar to Deville’s benzene. Thus, Cahors named the isolated compound toluene in 1850.
Properties of Toluene:
- The chemical formula of toluene is C6H5CH3.
- The boiling point of toluene is 111 oC.
- The melting point of toluene is −95 oC.
- The density of toluene is 0.87 g/mol.
- The molecular weight of toluene is 92.141 g/mol.
- Toluene reacts as an aromatic hydrocarbon in an electrophilic aromatic substitution reaction. This is because the methyl group has greater electron-releasing properties than a hydrogen atom in the exact same position.
- Toluene is more reactive than benzene toward electrophiles.
- Toluene undergoes sulfonation and as a result of that, it gives p-toluene sulfonic acid, and chlorination by Cl2 in the presence of FeCl3 to provide ortho and para isomers of chlorotoluene.
- Though the methyl side chain in toluene is susceptible to oxidation, toluene reacts with potassium permanganate to produce benzoic acid and with chromyl chloride to yield benzaldehyde, like the Etard reaction.
Production of Toluene
Toluene appears naturally in crude oil at low levels. It is a by-product in the production of gasoline by a catalytic reformer or ethylene cracker. Toluene is also a by-product of the production of coke from coal.
Preparation of Toluene In The Laboratory
Toluene is inexpensively made industrially. Toluene can be prepared by a variety of methods. For instance, although only of didactical interest, benzene reacts with methyl chloride in the presence of a Lewis acid such as aluminium chloride to give toluene:
C6H5H+CH3Cl→C6H5CH3+HCl
These reactions are complicated by the polymethylation process because toluene is more susceptible to alkylation than benzene.
Uses of Toluene
1. The Precursor to Benzene and Xylene:
Toluene is primarily in used as a precursor to benzene via hydrodealkylation:
C6H5CH3+H2→C6H6+CH4
The other application involves its disproportionation to a mixture of benzene and xylene.
2. Nitration:
Nitration of toluene gives mono-, di-, and trinitrotoluene, all of which are broadly in use. Dinitrotoluene is the precursor to toluene diisocyanate. It is used for the manufacture of polyurethane foam. Trinitrotoluene is an explosive typically abbreviated as TNT.
3. Oxidation:
Benzoic acid and benzaldehyde are manufactured commercially by the partial oxidation of toluene with oxygen. The catalysts include cobalt or manganese naphthenates.
4. Fuel:
Toluene is used as an octane booster in gasoline fuels for internal combustion engines as well as jet fuel. Toluene, at 86 percent by volume, fueled all the turbocharged engines in Formula One during the 1980s.
It was first pioneered by the Honda team. The remaining 14 percent was a file of n-heptane. It is to reduce the octane to meet Formula One fuel restrictions.
Toluene, at 100 percent, is used as a fuel for both two-stroke and four-stroke engines. Toluene is a good fuel.
Due to the density of the fuel and other factors, the fuel does not vaporise easily unless it is preheated to 70 oC or 158 oF.
In Australia, toluene was found to have been illegally mixed with petrol in fuel outlets for sale, as it was meant as a standard vehicular fuel.
Toluene incurs no fuel excise tax, though other fuels are taxed at more than 40 percent. It provides a greater profit margin for fuel suppliers.
Frequently Asked Questions
What is the effect of intermolecular forces on the boiling point?
The strength/potency of intermolecular forces (and thus the effect on boiling points) is ionic > nonionic. dispersion > dipole dipole > hydrogen bonding
Give a basic difference between intermolecular forces and intramolecular forces.
The forces that keep atoms together within a molecule are known as intramolecular forces, while the forces that exist between molecules are referred to as intermolecular forces.
What are the intermolecular forces, from weakest to strongest?
In the order of weakest to strongest:
- dispersion force.
- Dipole-dipole force.
- Hydrogen bond.
- Ion-dipole force.
Final Words
Toluene intermolecular forces refer to the different forces of attraction and interactions that exist between various molecules of toluene.
These forces are van der Waals forces, dipole-dipole interactions, and hydrogen bonding. These interactions play a substantial role in distinguishing the physical and chemical properties of toluene, such as its boiling point, melting point, and solubility.
