Catalyzes the conversion of (9Z,11E,15Z)-(13S)-hydroperoxyoctadeca-9,11,15-trienoate to (9Z)-12-oxo-dodec-9-enoate and cis-3-hexenal. Possesses low activity toward (9Z,11E)-(13S)-13-hydroperoxyoctadeca-9,11-dienoate (PubMed:9701595, PubMed:16258015). Required for the synthesis of the green leaf volatiles (GLVs) hexanal and trans-2-hexenal (PubMed:16258015). Expressed in roots, leaves, flowers and siliques. By wounding. No visible phenotype under normal growth conditions, but plants lacking HPL1 cannot synthesize the green leaf volatiles (GLVs) hexanal and trans-2-hexenal. Belongs to the cytochrome P450 family. In cv. Columbia, CYP74B2 (AC B3LF83) DNA sequence contains a 10-bp deletion that leads to a shorter N-terminus compared to typical other CYP74B subfamily members, and CYP74B2 is thought to be a non-functional enzyme. Functional alleles, with full N-terminus are found in cv. Landsberg erecta and cv. Wassilewskija (AC Q9ZSY9).