Using If/Truth Statements with pandas

I tried referencing the pandas documentation but still can't figure out how to proceed.

I have this data

In [6]:

df
Out[6]:
    strike putCall
0       50       C
1       55       P
2       60       C
3       65       C
4       70       C
5       75       P
6       80       P
7       85       C
8       90       P
9       95       C
10     100       C
11     105       P
12     110       P
13     115       C
14     120       P
15     125       C
16     130       C
17     135       P
18     140       C
19     145       C
20     150       C

and am trying to run this code:

if df['putCall'] == 'P':
    if df['strike']<100:
        df['optVol'] = 1
    else:
         df['optVol'] = -999       
else:
    if df['strike']>df['avg_syn']:
        df['optVol'] = 1
    else:
         df['optVol']= =-999

I get an error message:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

the above code and data are example only to illustrate the problem I ran into

Any assistance would be appreciated.

John