Chapter 20, Problem 4STP

Interpretation Introduction

Interpretation: The correct name for the skeletal structure $\text{C}-\text{C}-\text{C}=\text{C}$ needs to be determined.

Concept introduction:Cathode ray experiment: Beam of electrons are emitted from a cathode and observed in a vacuum tube.

Answer to Problem 4STP

The electron beams can be deflected by a capacitor or coil in a way which cause it to display an image on the screen.

Explanation of Solution

Rules for Naming Alkanes

1. Find the longest continuous chain of carbon atoms. This chain (called the parent chain) determines the base alkane name.
2. Number the carbons in the parent chain, starting at the end closest to any branching (the first alkyl substituent). When a substituent occurs the same number of carbons from each end, use the next substituent (if any) to determine from which end to start numbering.
3. Using the appropriate name for each alkyl group, specify its position on the parent chain with a number.
4. When a given type of alkyl group occurs more than once, attach the appropriate prefix (di- for two, tri- for three, and so on) to the alkyl name.
5. The alkyl groups are listed in alphabetical order, disregarding any prefix.

Therefore, the structure for $\text{C}-\text{C}-\text{C}=\text{C}$ is $\begin{array}{l}\text{H}\text{H}\text{H}\text{H}\\ \left|\right|\left|\right|\\ \text{H}-\text{C}-\text{C}-\text{C}=\text{C}\\ \left|\right|\left|\right|\\ \text{H}\text{H}\text{H}\text{H}\end{array}$ and the correct name is 1-butene because in this case you count from the right, and the double bond is after the first carbon.

Conclusion

The longest chain of this molecule has four carbons, so the root name is butene