Textbook Question
Compute the empirical and molecular formulas for each of the following elemental analyses. In each case, propose at least one structure that fits the molecular formula.
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Ch.1 - Structure and Bonding
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 1, Problem 14a
Compute the empirical and molecular formulas for each of the following elemental analyses. In each case, propose at least one structure that fits the molecular formula.
Verified step by step guidance1
Convert the percentage composition of each element to grams, assuming a 100 g sample. This gives 40.0 g of C and 6.67 g of H.
Convert the mass of each element to moles by dividing by their respective atomic masses: C (12.01 g/mol) and H (1.008 g/mol).
Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated.
Use the empirical formula to calculate the empirical formula mass. Compare this with the given molecular weight (MW = 90) to find the ratio of the molecular formula to the empirical formula.
Multiply the subscripts in the empirical formula by this ratio to obtain the molecular formula. Propose a structure that fits this molecular formula, considering common organic structures.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Empirical Formula
The empirical formula represents the simplest whole-number ratio of atoms in a compound. To determine it, convert the percentage composition of each element to moles by dividing by the atomic mass, then divide each by the smallest number of moles to find the ratio. This formula does not necessarily reflect the actual number of atoms in a molecule but provides the simplest ratio.
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How to use IHD with molecular formula.
Molecular Formula
The molecular formula indicates the actual number of each type of atom in a molecule. It is a multiple of the empirical formula. To find it, calculate the molar mass of the empirical formula and compare it to the given molecular weight (MW). The molecular formula is obtained by multiplying the subscripts in the empirical formula by the ratio of the molecular weight to the empirical formula weight.
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Proposing Molecular Structures
Proposing a molecular structure involves using the molecular formula to suggest possible arrangements of atoms that satisfy the formula. Consider the valency and bonding preferences of each element, and use known structural motifs and functional groups to propose plausible structures. This step often requires knowledge of organic chemistry principles, such as hybridization and resonance.
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Related Practice
Textbook Question
Compute the empirical and molecular formulas for each of the following elemental analyses. In each case, propose at least one structure that fits the molecular formula.
3
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Textbook Question
Draw line-angle structures for the compounds (a) through (h).
e. (CH3)3CCOCHCH2
f. CH3COCOOH
2
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Textbook Question
Draw line-angle structures for the compounds (a) through (h).
g. (CH3CH2)2CO
h. (CH3)3COH
1
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Textbook Question
Compute the empirical and molecular formulas for each of the following elemental analyses. In each case, propose at least one structure that fits the molecular formula.
3
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Textbook Question
Draw line-angle structures for the compounds (a) through (h).
c. CH3CH2COCN
d. CH2CHCHO
4
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