Ortho-nitrophenol L and para-nitrophenol L \(\mathrm{N}_{2}\) have different acidities, melting points, and boiling points. In all cases, the ortho- nitrophenol has lower values in these areas. Why?

Short Answer

Expert verified
Ortho-nitrophenol has lower acidity, melting point, and boiling point values compared to para-nitrophenol due to structural differences that affect intra- and inter-molecular forces. The nitro group in ortho-nitrophenol is closer to the hydroxyl group, allowing for better stabilization of negative charge and greater acidity. Additionally, ortho-nitrophenol exhibits intramolecular hydrogen bonding within the molecule, while para-nitrophenol forms intermolecular hydrogen bonds with other molecules. Since intermolecular forces are generally stronger than intramolecular forces, para-nitrophenol exhibits higher boiling and melting points.

Step by step solution

01

Understand the structure of ortho-nitrophenol and para-nitrophenol

Both ortho-nitrophenol and para-nitrophenol consist of a phenol group (a benzene ring with an attached hydroxyl group (OH)) and a nitro group (NO2). In ortho-nitrophenol, the nitro group is adjacent to the hydroxyl group, whereas in para-nitrophenol, the nitro group is opposite (at the other end of the benzene ring) the hydroxyl group.
02

Evaluate the acidity of these compounds

Acidity is determined by the stability of the anion formed after donating a proton. In both isomers, after losing an H+ ion from the hydroxyl group, the negative charge is delocalized into the benzene ring and the nitro group. However, in ortho-nitrophenol, the nitro group is closer to the negative charge and can better stabilize that charge through resonance. This makes ortho-nitrophenol more stable and consequently more acidic than para-nitrophenol.
03

Understand the impact of intramolecular hydrogen bonding on boiling and melting points

Boiling and melting points depend on the strength of the intermolecular forces. Stronger intermolecular forces lead to higher boiling and melting points. In the case of these isomers, the type of hydrogen bonding plays a significant role. In the case of ortho-nitrophenol, intramolecular hydrogen bonding happens within the molecule between the nitro group and the hydroxyl group due to their proximity. On the other hand, para-nitrophenol, because of the distance between the nitro and hydroxyl groups, can form intermolecular hydrogen bonding with other molecules.
04

Discuss the effect of intermolecular forces on boiling and melting points

Intermolecular forces are generally stronger than intramolecular forces. Therefore, compounds with intermolecular hydrogen bonding, like para-nitrophenol, will have higher boiling and melting points. The intramolecular hydrogen bonding in ortho-nitrophenol can't prevent molecules from separating as effectively as the intermolecular hydrogen bonding in para-nitrophenol. This is why ortho-nitrophenol has lower boiling and melting points. So, in conclusion, the structural differences in ortho- and para-nitrophenol lead to differences in their acidity, boiling points, and melting points.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

See all solutions

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free