$1.$Determine a structure for the following compounds. Assign each peak and explain the coupling observed. $($The IR shows a carbonyl peak$)$

$4.$Analyze the following multiplet, which is related to the hydrogen of a structural feature commonly found in organic molecules:

a$)$ Is it centrosymmertric?

b$)$ Are internal peaks an integral multiple intensity of the outer peak?

c$)$ Is the total intensity of all peaks a power of $2?$

d$)$ Is there a strict regularity of spacing?

e$)$ Identify the smallest coupling first.

f$)$ When you identify a coupling constant $J,$ does every peak in the multiplet have a mutual partner $JHz$ away to the left or right of it$?$

g$)$ Indicate the splitting and coupling with all $J$ values

h$)$ What common structure feature is this hydrogen found in$?$

$3.$ The following two peaks $($A and B$)$ represent a single hydrogen in the spectrum of iodocyclohexane taken at $-80C.$

a$)$ Why are two separate peaks seen for the same hydrogen at low temperature?

b$)$ Assign the stereochemistry of the hydrogen for each peak and indicate the coupling. Explain.

c$)$ At room temperature, what would you

expect to see for this hydrogen? Explain.

$2.$ How can you tell if two closely spaced lines are chemically shifted or coupled? It is not always possible to distinguish by the apperance of the spectrum.