[dazvoz]

NHCH2: this imine, to the best of my knowledge, exists as a hybrid with a radical. But what is it called? I get different answers from various online resources.

NIST calls it methanimine.
http://webbook.nist.gov/cgi/cbook.cgi?ID=C2053294&Units=SI


Chemspider calls in methenamine.
http://www.chemspider.com/Chemical-Structure.109754.html

Other sources call it methyleneimine.

What's the systematic name?

Would there be any such thing as  NHCHCl, or NHCHOH? I don't find any references to them so I guess the answer is no, so my follow up question be why not? I DO find references to compounds with chloro- or hydroxy- on the N, eg NClCH2, BUT not on the C.

Thanks in advance for your help.

[phth]

methyleneimine is probably informal my guess is formimine (formaldehyde-aldehyde+imine).  The adding a hydroxyl will tautomerize to the amide fyi.  If u want IUPAC you can just look things up by their CAS number; if you have access to ChemDraw, there is a built in algorithm to check your work generating IUPAC names. this may be a useful resource: http://goldbook.iupac.org/I02957.html

[dazvoz]

Thanks very much for that. That's a great resource.