In order to study the as yet little known functions of ARN non messengers, it is important to determine its secondary and tertiary structures. The SHAPE (Selective 2'-Hydroxylacylation Analyzed by Primer Extension), method, describes for the first time by K.M. Weeks' team in 2005, provides an easy, quick and quantitative measure for the environment of each nucleotide (whether paired or not/flexible conformation), allowing the determination of the secondary structure of the ARN. However, the results obtained are not always that clear. Furthermore, the acylation results of the SHAPE method are not always rationalized and, to our knowledge, no team has yet tried to understand the SHAPE mechanism. Current literature accepts that the SHAPE mechanism is based exclusively upon the acylation in ribose position 2' by electrophile agents, a mechanism proposed by previous work on acylation of mononucleotides, in a highly alkaline environment without determining the through RMN. Given that there exists several nucleophile sites on each nucleotide, our objective is to identify the resulting products of acylation in order to better understand the chemical mechanism for correctly interpreting the SHAPE results, and to design more selective chemical probes.