The compound shown below is responsible for the odor in rancid butter. Identify the functional group circled. 
Definitions:
Death Penalty
A legal punishment where an individual is executed by the state as retribution for a particularly severe crime.
Offender
An individual who has committed a violation of the law or a rule.
Victim
An individual who suffers harm or loss as a result of a crime, accident, or other event or action.
Comprehensive Crime Act
Legislation intended to address multiple facets of crime and criminal justice, often including preventative measures, law enforcement powers, sentencing, and rehabilitation.
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