When to use Case or IF statement to test for multiple conditions

I have a drop down that I am trying to test for multiple conditions. I have tried both an If and Case statement but keep getting errors...

This is what I have at this point and it still is kicking back syntax errors. I will have another condition to setup after this one but I think if I get this one figured out the other will work as well

Case([Est Month To Close],
"April",Q1,
"May",Q1,
"June",Q1,
"July",Q2,
"August",Q2,
"September",Q2,
"October",Q3,
"November",Q3,
"December",Q3,
"January",Q3,
"February",Q4,
"March",Q4,
)

Thanks in advance for the help