Log out Go to App
Go to App

Learning Materials

Features

Discover

Chapter 1: Problem 7

Carbon - oxygen bond lengths in formic acid are \(1.23 \mathrm{~A}^{\circ}\) and \(1.36 \mathrm{~A}^{\circ}\) respectively. \(\mathrm{H}-\mathrm{C}_{1} \quad\) However, both the carbon -oxygen bonds have the same value in the formate ion Rationalize.

Short Answer

Expert verified
Question: Explain the differences in carbon-oxygen bond lengths of formic acid and the formate ion. Answer: In formic acid, there is no resonance, so the carbon-oxygen double bond (C=O) is shorter than the carbon-oxygen single bond (C-O) resulting in different bond lengths. In the formate ion, resonance equalizes the bond lengths between the two carbon-oxygen bonds due to electron delocalization across the two oxygen atoms.

Step by step solution

01

Draw the Lewis structure of formic acid and formate ion

First, we need to draw the Lewis structures of formic acid (HCOOH) and the formate ion (HCOO-). Remember, in a Lewis structure, we represent chemical bonds by lines between the atoms involved, with each line representing a shared pair of electrons. Formic acid (HCOOH): O || H--C--O--H Formate ion (HCOO-): O- | H--C--O |
02

Identify resonance structures

Next, we need to determine if there are any resonance structures for formic acid and the formate ion. Resonance structures are different Lewis structures that represent the same compound, where the overall distribution of electrons is different in each structure, but the overall charge and connectivity remain the same. For formic acid, there is no resonance, as there are no other possible structures with the same connectivity and charge. For the formate ion, we find two resonance structures as follows: O- | H--C--O (Resonance Structure 1) | and O || H--C--O- (Resonance Structure 2)
03

Explain the effect of resonance on bond length

Resonance occurs when multiple valid Lewis structures can represent a compound, and the true structure is an average or hybrid of these different forms. The presence of resonance usually leads to a delocalization of electrons, which affects the bond lengths in the molecule or ion. In the case of formic acid, there is no resonance, and the carbon-oxygen double bond (C=O) is shorter than the carbon-oxygen single bond (C-O). That is why the bond lengths in formic acid are \(1.23 \mathrm{~A}^{\circ}\) for C=O and \(1.36 \mathrm{~A}^{\circ}\) for C-O. However, in the formate ion, there is resonance between the two structures, so the electrons in the carbon-oxygen bonds are delocalized between the two oxygen atoms. This equalizes the bond lengths between the two carbon-oxygen bonds, making them have the same value in the formate ion.
04

Conclusion

The different bond lengths of carbon-oxygen bonds in formic acid can be explained by the lack of resonance, resulting in distinct single and double bonds. On the other hand, the equal bond lengths in the formate ion can be rationalized by the presence of resonance, which leads to the equalization of bond lengths due to the delocalization of electrons across the two oxygen atoms.

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.

Start your free trial

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

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Lewis Structures
Understanding Lewis structures is fundamental to studying molecular geometry and bonding. A Lewis structure is a diagram that shows the bonding between atoms in a molecule as well as the lone pairs of electrons that may exist. These structures help us predict the number of bonds an atom can form, the arrangement of these bonds, and the presence of non-bonding electron pairs.

In the case of formic acid (HCOOH) and the formate ion (HCOO-), drawing the Lewis structures illustrates the different bonding scenarios. While the structure for formic acid has distinct single and double bonds to oxygen, the formate ion exhibits a scenario where we can draw two valid Lewis structures. These various representations provide the basis for understanding concepts such as resonance and bond length variation within these species.
  • Formic acid (HCOOH) has a double bond to one oxygen and a single bond to another.
  • The formate ion (HCOO-) has two structures that suggest an equal sharing of the additional electron density between the two oxygens.
Carbon-Oxygen Bond Length
The carbon-oxygen bond length in a molecule is pivotal in determining its chemical properties and reactivity. Bonds can be single, double, or triple, with single bonds being the longest and triple bonds, the shortest. This is due to the increased number of shared electrons in multiple bonds, pulling atoms closer together.

For example, formic acid has two carbon-oxygen bonds of different lengths, a shorter double bond and a longer single bond. These differences in lengths are typical when no resonance is present — each bond type has a distinct length based on its electron sharing. In formate ion, however, resonance causes the electron density of the single and double bonds to spread out over both oxygen atoms, leading to two bonds with equal length, quite unique and different from formic acid.
  • Formic acid exhibits typical single and double bond lengths.
  • Formate ion displays equalized bond lengths due to resonance.
Formic Acid and Formate Ion
Formic acid and the formate ion are interrelated species, with the formate ion being the deprotonated form of formic acid. They are both simple and common examples used to demonstrate fundamental concepts in resonance and acidity in chemistry.

The formate ion arises from formic acid when it donates a hydrogen ion (proton) and becomes negatively charged. This ionization leads to interesting changes in the electron structure, as covered in the resonance and Lewis structures sections. Though these two chemical species are structurally similar, their electron configurations and properties differ significantly due to this ionic change.
  • Formic acid consists of a hydrogen atom attached to a carboxyl group.
  • The formate ion, after losing a proton, gains a negative charge and exhibits resonance.
Delocalization of Electrons
Delocalization of electrons refers to the phenomenon where electrons are not associated with a single atom or bond, but are spread out over several adjacent atoms. This can occur in structures that have resonance, when the electrons involved in bonding are distributed over two or more atoms, effectively 'averaging' the bonds.

In the formate ion, we observe delocalization as it has two resonance structures that contribute to the final hybrid structure. This results in an equal distribution of electron density over the two carbon-oxygen bonds, making them equivalent in length and character. It is the reason why the formate ion does not have a typical single and double bond, unlike formic acid, where the electrons are localized in distinct bonds.
  • Delocalization results in the stabilization of the molecular structure.
  • The concept is critical for understanding the bonding and reactivity of molecules with resonance such as the formate ion.

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

Directions: Each question contains Statement- 1 and Statement-2 and has the following choices (a), (b), (c) and (d), out of which ONLY ONE is correct. (a) Statement- 1 is True, Statement- 2 is True; Statement- 2 is a correct explanation for Statement- 1 (b) Statement- 1 is True, Statement- 2 is True; Statement- 2 is NOT a correct explanation for Statement-1 (c) Statement- 1 is True, Statement- 2 is False (d) Statement- 1 is False, Statement- 2 is True Statement 1 Stereoisomers which do not have an object and mirror image relationship can be termed as diastereomers. and Statement 2 An organic compound having only one chiral centre cannot have diastereoisomers.

The boiling point of \(\mathrm{CH} 3 \mathrm{OH}\) is \(65^{\circ} \mathrm{C}\), while the boiling point of \(\mathrm{CH} 3 \mathrm{SH}\) is only \(6^{\circ} \mathrm{C}\). Explain this difference in boiling point.

An allylic carbocation is less stable than (a) a vinyl cation (b) neopentyl cation (c) benzylic cation (d) \(\mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{2}-\mathrm{CH}_{2}^{+}\)

Which of the following is not true about a homolytic fission? (a) The products are free radicals. (b) The reaction occurs under the influence of heat or light. (c) It occurs when the bond breakage is between two atoms of the same electronegativity. (d) Intermediates may undergo rearrangement.

A chemical reaction is one in which old bonds are broken and new bonds are made. During the course of these changes a variety of intermediates are formed before a starting material is converted to final products. Formation of these intermediates depend on several factors like bond energies, kinetics of the reactions etc. In which of the following choices, the correct order is not indicated. (a) \(\mathrm{F}^{-}<\mathrm{Cl}^{-}<\mathrm{Br}^{-}<\mathrm{I}^{-}(\) the order of base strength \()\) (b) \(\mathrm{ClCH}_{2} \underset{\oplus}{\mathrm{C}}\left(\mathrm{CH}_{3}\right)_{2}<\left(\mathrm{CH}_{3}\right)_{3} \mathrm{C}<\left(\mathrm{CH}_{3}\right)_{2} \mathrm{COCH}_{3}\) (stability of carbocation) (c) \(\mathrm{O}_{2} \mathrm{~N}-\mathrm{CH}_{2}>\mathrm{CH}_{3}>\mathrm{CH}_{3} \mathrm{CH}_{2}\) (stability of carbanion) (d) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2}<\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}<\left(\mathrm{CH}_{3}\right)_{2} \mathrm{C}=\mathrm{C}\left(\mathrm{CH}_{3}\right)_{2}\) (stability of alkenes)
See all solutions

Recommended explanations on Chemistry Textbooks

Physical Chemistry

Read Explanation

Chemistry Branches

Read Explanation

Kinetics

Read Explanation

The Earths Atmosphere

Read Explanation

Organic Chemistry

Read Explanation

Nuclear Chemistry

Read Explanation
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