Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

2. Molecular Representations

Functional Groups

Organic Chemistry

2. Molecular Representations

Functional Groups

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3:36 minutes

Problem 46h

Textbook Question

Given the line-angle drawings shown, answer the following questions:
(i) How many carbons are in each molecule?
(ii) How many hydrogens are at the circled carbon?
(iii) Is the indicated (→) carbon or 1° , 2°, 3°, or 4°?
(h)

Verified step by step guidance

Step 1: Analyze the line-angle drawing to determine the number of carbons in each molecule. In line-angle drawings, each vertex or endpoint represents a carbon atom unless otherwise specified. Count all the vertices and endpoints to find the total number of carbons.

Step 2: For the circled carbon, determine the number of hydrogens attached. Recall that carbon typically forms four bonds. Subtract the number of bonds already shown (to other atoms) from four to calculate the number of hydrogens attached to the circled carbon.

Step 3: Examine the indicated (→) carbon to determine its degree of substitution. A carbon is classified as: 1° (primary) if bonded to one other carbon, 2° (secondary) if bonded to two other carbons, 3° (tertiary) if bonded to three other carbons, and 4° (quaternary) if bonded to four other carbons.

Step 4: Verify your answers by carefully reviewing the line-angle drawing and ensuring that all bonds and implied hydrogens are accounted for. Double-check the degree of substitution for the indicated carbon.

Step 5: Summarize your findings for each part of the question: (i) the total number of carbons in each molecule, (ii) the number of hydrogens at the circled carbon, and (iii) the degree of substitution (1°, 2°, 3°, or 4°) for the indicated carbon.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Line-Angle Structures

Line-angle drawings, also known as skeletal structures, are a shorthand representation of organic molecules. In these diagrams, vertices represent carbon atoms, and the ends of lines represent terminal carbon atoms. Hydrogen atoms are typically omitted for clarity, as they are implied based on carbon's tetravalency. Understanding how to interpret these drawings is essential for determining the number of carbon and hydrogen atoms in a molecule.

Degree of Carbon Atoms

The degree of a carbon atom refers to the number of other carbon atoms directly bonded to it. A carbon can be classified as primary (1°) if it is attached to one other carbon, secondary (2°) if attached to two, tertiary (3°) if attached to three, and quaternary (4°) if attached to four. This classification is crucial for understanding the reactivity and stability of the molecule, as different degrees influence chemical behavior.

Hydrogen Count at Specific Carbons

The number of hydrogen atoms bonded to a carbon atom can be determined by considering the carbon's tetravalency, which states that carbon forms four bonds. The number of hydrogen atoms attached to a carbon depends on how many other atoms (including carbon) are bonded to it. For example, a primary carbon typically has three hydrogens, while a tertiary carbon has only one. This concept is vital for answering questions about specific carbons in a molecule.

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Related Practice

Textbook Question

Identify the functional groups in each of the following molecules. [The number of functional groups has been given to assist you.]

(d) [Two]

Textbook Question

Identify the functional groups in each of the following molecules. [The number of functional groups has been given to assist you.]

(b) [Two]

Textbook Question

Identify the functional groups in each of the following molecules. [The number of functional groups has been given to assist you.]

(a) [Three]

Textbook Question

When we begin studying reactive intermediates, the designation of substitution will be especially important. Label the following carbocations as 1° , 2°, 3°, or 4° or based on the carbon bearing the positive charge.

(c)

Textbook Question

Identify the functional groups in each of the following molecules. [The number of functional groups has been given to assist you.]

Textbook Question

(b)

Textbook Question

Classify each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).

c. 2-methylbutane

d. cyclohexane

Textbook Question

Label each hydrogen atom in the following compounds as primary (1°), secondary (2°), or tertiary (3°).

(e)

(f)

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Given the line-angle drawings shown, answer the following questions:(i) How many carbons are in each molecule?(ii) How many hydrogens are at the circled carbon?(iii) Is the indicated (→) carbon or 1° , 2°, 3°, or 4°?(h)

Key Concepts

Line-Angle Structures

Degree of Carbon Atoms

Hydrogen Count at Specific Carbons

Watch next

Given the line-angle drawings shown, answer the following questions:
(i) How many carbons are in each molecule?
(ii) How many hydrogens are at the circled carbon?
(iii) Is the indicated (→) carbon or 1° , 2°, 3°, or 4°?
(h)