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°?
(e)

Verified step by step guidance

1. Step 1: Count the number of carbons in the molecule. In a line-angle drawing, each vertex represents a carbon atom. For the given cyclic structure, count the vertices to determine the total number of carbons.
2. Step 2: Determine the number of hydrogens at the circled carbon. In a line-angle drawing, hydrogens are implied based on the number of bonds a carbon atom has. Carbon typically forms four bonds, so subtract the number of bonds shown from four to find the number of hydrogens attached to the circled carbon.
3. Step 3: Analyze the indicated (arrowed) carbon to determine its degree. The degree of a carbon atom is based on the number of other carbon atoms it is directly bonded to: 1° (primary) for one bond, 2° (secondary) for two bonds, 3° (tertiary) for three bonds, and 4° (quaternary) for four bonds.
4. Step 4: Verify the structure and ensure all implied hydrogens and bonds are accounted for. Double-check the circled and indicated carbons to confirm their properties.
5. Step 5: Summarize the findings for each part of the question: (i) total carbons, (ii) hydrogens at the circled carbon, and (iii) degree of the indicated carbon.

Key Concepts

Line-Angle Drawings

Line-angle drawings, also known as skeletal structures, are a shorthand representation of organic molecules. In these drawings, vertices represent carbon atoms, and the ends of lines represent carbon atoms as well. Hydrogen atoms are typically omitted for clarity, as they are implied based on the carbon's tetravalency. Understanding this notation is crucial for determining the number of carbons and hydrogens in a molecule.

Degree of Carbon

The degree of a carbon atom refers to the number of other carbon atoms it is directly bonded to. A carbon can be classified as primary (1°), secondary (2°), tertiary (3°), or quaternary (4°) based on this bonding. This classification affects the reactivity and properties of the molecule, making it essential to identify the degree of the indicated carbon in the question.

Hydrogen Count at a Carbon

The number of hydrogen atoms attached to a carbon atom depends on its degree and the presence of other substituents. A carbon atom typically forms four bonds; thus, a primary carbon (1°) is bonded to one other carbon and has three hydrogens, while a tertiary carbon (3°) is bonded to three other carbons and has only one hydrogen. Accurately counting the hydrogens at the circled carbon is vital for understanding the molecule's structure.