what purpose might steinbeck have beginning the chapter with only lennie in the barn and ending it with only candy

This is interesting. Lennie and candy share the theme of loneliness but in different ways. Although Lennie has George he spends much time by himself alone and isolated from the "able" world. Candy has discourse with other people but feels isolated by age and physical breakdown. I'm not sure how a barn factors into this but it is a large seemingly empty space. Here animals are separated from people so perhaps some inferences could be made from this.