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In chemistry, sulfonation, sometimes known as Sulphonation, refers to any of the various ways for producing sulfonic acids. Sulfonation procedures include the reactions of aromatic hydrocarbons with sulfuric acid, chlorosulfonic acid, or sulphur trioxide, the reactions of organic halogen compounds with inorganic sulfites, and the oxidation of certain classes of organic sulphur compounds, particularly disulfides and thiols.
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Key Terms: Sulfonation, sulphur, substitution reactions, organic compounds, oxidation, sulphur trioxide, sulfuric acid, chlorosulfonic acid, hydrocarbons
What is Sulphonation?
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The process of replacing a hydrogen atom with a sulfonic acid group, SO3H, is known as sulphonation. Sulphonation of a typical alkane, starting with hexane, can be accomplished by treating the alkane with oleum (fuming sulphuric acid). In the instance of hydrogen atom replacement, tertiary is much greater than secondary, and secondary is much greater than primary; replacement of a primary hydrogen atom in sulphonation is extremely slow. Isobutane, which has a tertiary hydrogen atom, is easily sulfonated to produce t-butyl sulfonic acid:
(CH3)3CH + H2SO4/SO3 → (CH3)3CSO3H + H2SO4
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| Class 12 Chemistry Related Concepts | ||
|---|---|---|
| Etard reaction | Williamson Ether Synthesis | Electrophilic Aromatic Substitution |
| Ester Hydrolysis | Reimer Tiemann Reaction | Esterification |
Mechanism of Sulphonation
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This is not settled, due in part to the difficulties in determining the nature of the sulfonating species (cf. nitration). Thus, several options for sulphonation with concentrated sulphuric acid exist, each resulting from a different equilibrium, e.g.,
- 2H2SO4 -> SO3 + H3O+ +HSO4-
- SO3 + H2SO4 -> H2SO4(SO3) or H2S2O7
- 3H2SO4 -> SO3H+ + H3O+ + 2HSO4-
External research based on kinetic measurements in concentrated sulfuric acid and oleum supports the notion that the active species is sulphur trioxide. This is also thought to be true for aqueous sulphuric acid. If we accept this, it appears that the order of the stages and their relative rates are conditional. Thus, with concentrated sulphuric acid, the proposed mechanism is:
In oleum, on the other hand, the hypothesized process is:
When sulphur trioxide is used in an organic solvent, the data suggest that the mechanism is different from those described above; for example, Cerfontain et al. (1968) report that sulfonation of p-dichlorobenzene with sulphur trioxide in nitromethane proceeds as follows:
In addition to the issues outlined above, the fact that sulphonation is reversible and that isomerization happens frequently during the reaction complicates matters. Under different situations, these factors affect the isomer distribution. Wanders et al. (1963), for example, demonstrated that when heated in aqueous sulphuric acid, toluene-p- and m-sulphonic acid isomerize to generate a mixture primarily of m- and p-sulfonic acid with only a trace of the o-isomer. Also, the o-isomer rapidly isomerizes to the p-isomer, but the equilibrium mixture remains the same (i.e., all three isomers). Based on these findings, it appears that toluene-m-sulphonic acid is the most thermodynamically stable isomer, while o-acid is the least.
Sulfonation of Benzene
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Sulfonation of benzene is the process of heating benzene with fuming sulphuric acid (H2SO4 + SO3) to generate benzenesulfonic acid. This reaction, depicted below, is reversible in nature.
Sulfonation of Benzene
Sodium Xylenesulfonate
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A hydrotrope is an organic chemical that improves water's capacity to dissolve other molecules. A hydrotrope is sodium xylene sulfonate. Sodium xylene sulfonate is classed as a low-hazard compound, and the risk of adverse health consequences from consumer and occupational usage is predicted to be negligible.
Uses and Applications Sodium Xylenesulfonate
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Sodium xylene sulfonate can be found in shampoos and liquid household detergents, as well as printing pastes and textile degreasing compounds. It is also a surfactant found in personal care products, primarily shampoos, due to its capacity to act as a wetting agent or Clariant, allowing a formula to spread fast. Sodium xylene sulfonate can be used to remove lignin and pentosans from paper, and it can also be utilized as a glue component in the leather industry.
- Sulphonation Reaction
Sulphonation is the process of replacing an organic compound's hydrogen atom with a sulfonic acid (-SO3H) functional group, usually through a reaction with sulfuric acid at higher temperatures.
"Sulphonation is the introduction of a sulfonic acid group into an aromatic molecule."
- Dodecylbenzenesulfonic Acid
A type of dodecylbenzene is dodecylbenzene. Sulfonic acid is a thick liquid that ranges in color from pale yellow to brown. It has the potential to be employed in the production of detergents. Dodecylbenzene Sulfonic acid is on the Hazardous Substance List because it has been cited by the EPA and the Department of Transportation. Because it is CORROSIVE, this compound is included on the Special Health Hazard Substance List.
- Sulphonation of Phenol
Sulphonation of phenol refers to the interaction of phenol with strong sulphuric acid. The operating temperature determines the sulphonation product.
Phenol interacts with concentrated H2SO4 at low temperatures to create o-phenol sulphonic acid. The nearby SO3H and OH groups interact with each other at low temperatures. As a result, ortho isomers predominate.
At high temperatures, none of the interactions can develop, therefore steric repulsion triumphs over attraction. As a result, p-phenol sulphonic acid can be produced at high temperatures. The rate of reaction for benzene and Hexa deuterobenzene changes due to sulphonation. Protium has one proton and no neutrons, as opposed to Deuterium, which has one neutron and is hence twice as heavy. Because of the mass difference, vibrations are smaller or the bond is stronger and shorter. As a result, a Carbon-Deuterium bond is stronger than a Carbon-Protium bond.
To determine the effect of this change in bond strength on the rate of an Electrophilic Aromatic Substitution, we must first examine the mechanism: The true electrophile in the sulfonation is supplied as SO3, as we can see. We have two steps: the production of the intermediate -complex (also known as the Wheland intermediate) and the subsequent shift of hydrogen (also known as Deuterium) to restore aromaticity. The first step involves the loss of aromaticity and is considered the slowest. The protium or Deuterium-bond is then broken in the second stage. As a result, the second step for Deuterium is projected to be slower than for Protium. We do not expect a genuine isotope effect because the initial stage is so slow. It turns out that there is no isotope impact in the nitration and bromination reactions; nevertheless, there appears to be an isotope effect in the sulfonation reaction (although it depends on the conditions).
To put it simply, this means that either the second step is the rate-determining step or something else is going on: This can be described in this way based on the fact - the first step can return to the original condition. k1 is the rate constant of the inverse reaction. We wouldn't expect to see a real difference between Protium and Deuterium in this inverse reaction. We would expect no isotope effect if the majority of the intermediate product progresses to the final reaction product k1k2. In contrast to circumstances when the reverse reaction is quicker or almost equivalent to the reaction towards the end product (hence, k1>k2), We would expect to see an isotopic influence in those circumstances.
Things to Remember
- The process of replacing a hydrogen atom with a sulfonic acid group, SO3H, is known as sulphonation.
- In the instance of hydrogen atom replacement, tertiary is much greater than secondary, and secondary is much greater than primary; replacement of a primary hydrogen atom in sulphonation is extremely slow.
- External research based on kinetic measurements in concentrated sulfuric acid and oleum supports the notion that the active species is sulphur trioxide. This is also thought to be true for aqueous sulphuric acid.
- Sulfonation of benzene is the process of heating benzene with fuming sulphuric acid (H2SO4 + SO3) to generate benzenesulfonic acid. This reaction, depicted below, is reversible in nature.
- A type of dodecylbenzene is dodecylbenzene. Sulfonic acid is a thick liquid that ranges in color from pale yellow to brown. It has the potential to be employed in the production of detergents.
- Sulphonation of phenol refers to the interaction of phenol with strong sulphuric acid. The operating temperature determines the sulphonation product.
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Sample Questions
Ques. What is a Linear Alkyl Benzene Sulphonic Acid? (1 mark)
Ans. Linear alkyl benzene sulphonic acids (LAS) are anionic surfactants. Linear alkyl benzene sulphonic acids are a mixture of sulphonic benzene acids with various lengths of linear alkyl chains (such as C9: below 1 percent, C10: 8 - 16 percent, C11: 26 - 38 percent, C12: 26 - 38 percent, C13: 15 - 27 percent and longer than C13: below 2.5 percent ).
Ques. Explain Why Alkanes Do Not Undergo Nitration? (1 mark)
Ans. Because there is no suitable low-temperature mechanism, they will nitrate under duress, and the nitrated product is likely to be more unstable and reactive than the original alkane.
Ques. What are Esters? (1 mark)
Ans. Esters are polar compounds, but due to the lack of hydrogen bound to oxygen, they lack the potential to form strong hydrogen bonds with one another. As a result, esters have lower boiling temperatures than alcohols or acids with identical molecular weights. Esters frequently have a pleasant odor that is responsible for the distinctive aromas of flowers, fruits, and so on.
Ques. What are Diethyl Ethers? (1 mark)
Ans. This is defined as an organic molecule in which two aryl groups, alkyl groups, or an aryl and alkyl group are attached to both sides of an oxygen atom (ROR|). Ethers can be symmetrical or unsymmetrical depending on their R groups. If both R groups are the same, the ether is symmetrical; if they are different, the ether is unsymmetrical. The simplest ether, for example, is diethyl ether.
Ques. What is sulfonation used for? (1 mark)
Ans. Sulfuric acid sulfonation is now mostly utilized to produce hydrotropes via an azeotropic reaction with benzene, toluene, or xylene. The water generated during the reaction is removed using azeotropic distillation of the water and unreacted material in this particular method.
Ques. What is the difference between sulfonation and sulfation? (1 mark)
Ans. Sulfonation and sulfation are two major chemical procedures used to add a sulfur-containing group to an organic molecule in numerous industries. The primary distinction between sulfonation and sulfation is that sulfonation results in the production of a C-S bond, whereas sulfation results in the formation of a C-O-S bond.
Ques. How does sulfonation occur? (1 mark)
Ans. Sulfonation is a reversible reaction that produces benzenesulfonic acid by combining sulphur trioxide and fuming sulfuric acid. To generate benzene, add hot aqueous acid to benzenesulfonic acid.
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