Obtenir is a french third group verb. So, this verb is irregular and do not follow a regular conjugation pattern like first or second group verbs. Follow this link to see all the endings of the conjugation of most of the third group verbs : 
conjugation rules and endings for the second group verbs.
																												
																																					Verbs derived from 
tenir and 
venir form a major group of verbs who gains a 
d in the future and conditional. These verbs are the only verb to have a nasal vowel in the past historic and imperfect subjunctive.																												
																																																																																																		
Obtenir is conjugated in interro-negative form. The interro-negative form being obtained by inversion of the subject, the placement of the negative adverb follow the same rules as in negative form, giving the following rules:
									
 - in interro-negative form, the adverb 
« ne » is always placed first if the subject is a pronoun.
									
 - in simple tenses, the adverbs (
« ne ...pas », 
« ne...plus », 
« ne...jamais », etc...) surround the verb 
obtenir and the inverted subject pronoun.
									
 - in compound tenses or in passive voice, the negative adverbs surround the auxiliary and the inverted subject pronoun.
																		
																			
For sound reasons, like in interrogative form, an euphonious 
« t » is added to the pronoun of the third person: 
« il », 
« elle », 
« on », 
« ils », 
« elles » except when the verb ends with 
« t » or 
« d »: 
« n'obtiendra-t-il pas ? », 
« n'a-t-il pas obtenu ? », 
« n'aura-t-il pas obtenu ? ».
																											
Finally, the interrogative form does not exist in subjunctive and imperative.