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Shweta Thakur posted an Question
June 18, 2020 • 04:41 am 30 points
  • IIT JAM
  • Chemistry (CY)

No3-and hso4- which is more stabilized by resonance and why hso4-is favourable for dehydration ....

no3-and hso4- which is more stabilized by resonance and why hso4-is favourable for dehydration

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    Dinesh khalmaniya 1 best-answer

    Conc. sulphuric acid (H2​SO4​) is a good dehydrating agent. On the other hand, hydrochloric acid (HCl) and nitric acid (HNO3​) are not dehydrating agents. In the case of HCl, Cl− is a strong nucleophile and will cause nucleophilic substitution reaction. Similarly, HNO3​ will cause oxidation reaction. However, in the presence of sulphuric acid, alcohols get protonated and then lose water to form alkene. CH3​−CH2​−OH⟶CH2​=CH2​+H2​O

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    Dinesh khalmaniya 1 best-answer

    Nitric and perchloric acids are sold at 70% aqueous, so most of their dehydrating ability has already been consumed, while sulfuric acid is sold as 98%. At 98% concentration, nitric and perchloric acids are likely to be very good dehydrating agents, but these are also very strong oxidizers, less stable, etc.

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    Dinesh khalmaniya 1

    hope this will help you 🙏

    eduncle-logo-app

    tell me also that why hno3 is not use in this reaction ..... I have sent u the 2 pages plz explain

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    Dinesh khalmaniya 1 Best Answer

    A dehydration reaction is an elimination reaction, which are always in competition with substitution reactions. You can control which will occur, depending on reaction conditions such as nature of nucleophile and solvent. For example, the presence of water can reverse a dehydration reaction - even if elimination occurs and a double bond is formed, water can end up hydrating across the double bond, thus yielding another alcohol. The net result is that you have dehydrating and hydrating reactions that compete against each other, and a substitution reaction. The reason sulfuric acid is used is because it is a dehydrating agent (not "dehydrating" as in removing an alcohol group along with a proton, but "dehydrating" as in it removes water in a solvent). All halide acids are aqueous solutions (e.g., concentrated HCl is 37%, or 12 M). This gives a large concentration of water in the solvent. Sulfuric acid, on the other hand, are commonly available as 98% solutions, making it a good dehydrating agent.

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