2-(chloromethyl)-1-nitroso-4,5-dihydro-1H-imidazole (O=NN1CCN=C1CCl)
Please provide the AI limits and CPCA score for the above compound.
Dear NNRUSP
If I am not mistaken CPCA is not applicable for imidazoles.
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The compound is not exactly imidazole, only one double bond is there in imidazole ring.
It should be Class 4 - 1500 ng/day
H-count: 0,2 - +3
part of a 5-member ring +2
Total score = 5
I attach the structure for ready reference
I have still concerns if CPCA could be applied.
Please note that according EMA Appendix 2,
CPCA applies to N-nitrosamines bearing a carbon atom on both sides of the N-nitroso group, and where the carbon is not directly double bonded to a heteroatom
Moreover, CPCA does not apply to N-nitrosamines where the N-nitroso group is attached to a nitrogen within a hetero aromatic ring.
I would welcome any feedback 
BR
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CPCA does not apply, as you describe, this is an “other nitroso” for which a classic nitrosamine mutagenicity mechanism is not predicted (which is the basis for CPCA, hence the exclusions in scope of CPCA based on structure as you describe).
For similar structures (1-nitroso-4,5-dihydro-1H-imidazole moiety), MNNG readacross is currently used in the other nitroso list of EMA and TGA.
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Dear ccdw
thank you for your response.
I was also of the idea of MNNG readacross - really happy to see that you agree!
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You are totally right, I missed that bit!
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You are right CPCA cannot be applied in this case.
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