| No. | CAS # | Product Names | Molecular Formula |
| 551 | 290-37-9 | Pyrazine | C4H4N2 |
| 552 | 288-13-1 | Pyrazole | C3H4N2 |
| 553 | 93697-74-6 | Pyrazosulfuron-ethyl | C14H18N6O7S |
| 554 | 98389-04-9 | Pyrazosulfuron | C12H14N6O7S |
| 555 | 121-21-1 | PYRETHRIN 1 | C21H28O3 |
| 556 | 121-29-9 | PYRETHRIN 2 | C22H27O5- |
| 557 | 88678-67-5 | Pyributicarb | C18H22N2O2S |
| 558 | 96489-71-3 | Pyridaben | C19H25ClN2OS |
| 559 | 37444-46-5 | Pyridazin-3-ylmethanol | C5H6N2O |
| 560 | 18820-82-1 | Pyridine hydrobromide | C5H5N.HBr;C5H6BrN |
| 561 | 628-13-7 | Pyridine hydrochloride | C5H5N.HCl;C5H6ClN |
| 562 | 26412-87-3 | Pyridine sulfur trioxide | C5H5N.SO3 |
| 563 | 464-05-1 | Pyridine trifluoroacetate | C5H5N.C2HF3O2 |
| 564 | 89-00-9 | Pyridine-2,3-dicarboxylic acid | C7H5NO4 |
| 565 | 5112-36-7 | Pyridine-2,6-dicarbohydrazide | C7H9N5O2 |
| 566 | 141-86-6 | Pyridine-2,6-diyldiamine | C5H7N3 |
| 567 | 1692-15-5 | Pyridine-4-boronic acid | C5H6BNO2 |
| 568 | 26299-14-9 | Pyridinium chlorochromate | C5H5N.HCrO3Cl |
| 569 | 20039-37-6 | Pyridinium dichromate | 2(C5H5N).H2Cr2O7 |
| 570 | 39416-48-3 | Pyridinium tribromide | C5H6Br3N |
| 571 | 853645-22-4 | Pyridoxal 5'-phosphate | C8H10NO6P |
| 572 | 54-47-7 | Pyridoxal phosphate | C8H10NO6P |
| 573 | 635-38-1 | Pyridoxine dipalmitate | C40H71NO5 |
| 574 | 58-56-0 | pyridoxine hydrochloride | C8H11NO3.HCl；C8H12ClNO3 |
| 575 | 65-23-6 | pyridoxine | C8H11NO3 |
| 576 | 58-14-0 | Pyrimethamine | C12H13ClN4 |
| 577 | 49647-58-7 | Pyrimidinetetramine sulfate | C4H8N6.H2SO4 |
| 578 | 289-95-2 | Pyrimidine | C4H4N2 |
| 579 | 95737-68-1 | Pyriproxyfen | C20H19NO3 |
| 580 | 123343-16-8 | Pyrithiobac-sodium | C13H10ClN2NaO4S |
| 581 | 120-80-9 | pyrocatechol | C6H6O2 |
| 582 | 87-66-1 | Pyrogallol | C6H6O3 |
| 583 | 2466-09-3 | Pyrophosphoric acid | H4P2O7 |
| 584 | 1003-29-8 | Pyrrole-2-carboxaldehyde | C5H5NO |
| 585 | 931-03-3 | Pyrrole-3-carboxylic acid | C5H5NO2 |
| 586 | 109-97-7 | Pyrrole | C4H5N |