3) please draw line angle formulas and provide iupac (systematic) names for the four (4) structural isomers…

Explanation:

Step1: Determine possible carbon - chain skeletons

The carbon - chain skeletons for 4 - carbon compounds can be a straight - chain or a branched - chain.

Step2: Place the bromine atom

For straight - chain isomers

1. When the carbon chain is straight ($C - C - C - C$), the bromine can be on the first carbon (1 - bromobutane) or the second carbon (2 - bromobutane). The line - angle formula for 1 - bromobutane: A straight chain with 4 vertices (carbons), and the bromine is attached to the first vertex. The line - angle formula for 2 - bromobutane: A straight chain with 4 vertices, and the bromine is attached to the second vertex.

For branched - chain isomers

The branched - chain has a carbon chain of the form $C - C(CH_3)-C$. The bromine can be attached to the central carbon (2 - bromo - 2 - methylpropane) or the terminal carbon (1 - bromo - 2 - methylpropane). The line - angle formula for 2 - bromo - 2 - methylpropane: A central vertex with 3 other vertices attached to it (forming a 'Y' - like shape), and the bromine is attached to the central vertex. The line - angle formula for 1 - bromo - 2 - methylpropane: A 'Y' - like shape with the bromine attached to a terminal vertex.

Answer:

1. 1 - bromobutane: Line - angle formula: A straight chain of 4 carbon atoms with Br on the first carbon; IUPAC name: 1 - bromobutane.
2. 2 - bromobutane: Line - angle formula: A straight chain of 4 carbon atoms with Br on the second carbon; IUPAC name: 2 - bromobutane.
3. 1 - bromo - 2 - methylpropane: Line - angle formula: A 'Y' - shaped structure with Br on a terminal carbon; IUPAC name: 1 - bromo - 2 - methylpropane.
4. 2 - bromo - 2 - methylpropane: Line - angle formula: A 'Y' - shaped structure with Br on the central carbon; IUPAC name: 2 - bromo - 2 - methylpropane.