This paper deals with optimal control problems for systems affine in the control variable. We have nonnegativity constraints on the control, and finitely many equality and inequality constraints on the final state. First, we obtain second order necessary optimality conditions. Secondly, we get a second order sufficient condition for the scalar control case. The results use in an essential way the Goh transformation.Key-words: Optimal control, second order conditions, control constraints, singular arc, bang-singular solutions Mots-clés : Commande optimale, conditions du second ordre, contraintes sur la commande, arc singulier, solutions bang-singulières.