Complex organic molecules (COMs, i.e. molecules with six or more atoms with at least one carbon) are present in the gas around young stars in the earliest stages of their evolution. Similar molecules are also found in meteorites and comets in our Solar System. Their formation may be closely related to the physical processes that led to the formation of the Solar System. Thus, it is important to study the chemistry of COMs around young protostars to understand how these molecules are formed, how they can form prebiotic molecules, such as amino acids, and investigate whether they potentially could be important for the origin of life elsewhere. In this thesis, the inventory of oxygen-bearing COMs towards a young protostellar binary is studied and their chemical formation and evolution discussed. The low-mass Class 0 protostellar binary IRAS 16293–2422, located in the ρ Ophiuchus molecular cloud, has been observed with the Atacama Large Millimeter/submillimeter Array (ALMA) as part of the “Protostellar Interferometric Line Survey (PILS)”. This well-studied sourceis characterised by its great molecular richness and their high abundance, especially in the innermost region of the envelope of each protostar, the so-called “hot corinos”. The high spectral resolution and the high sensitivity of the observations, revealed ∼10 000 lines belonging to more than 100 molecular species, including a number of rarer isotopologues of different COMs. The abundances of the oxygen-bearing COM were derived from their spectral features towards both components of the binary system. The comparison between the molecular abundances found towards two binary components and the spatial extent of the emission from different molecules suggests that the hot corino region has a layered structure in terms of its molecular composition. This layer-structure seems to be correlated with the desorption temperatures of the different species, i.e. that the molecules having a higher desorption temperature are located in the inner layers of the hot corino (closer to the central protostar), compared to molecules with lower desorption temperatures. The PILS observations allowed for several new detections of molecules in the interstellar medium, some of which are reported in this thesis. These include CHD2OCHO, a variant of methyl formate (CH3OCHO) where two hydrogen atoms are substituted by deuterium. The D/H ratio measured for CHD2OCHO is systematically higher than those estimated for the singly-deuterated isotopologues of methyl formate, CH2DOCHO and CH3OCDO. This deuteration enhancement is consistent with the higher D/H ratio of D2CO compared to HDCO, which are two molecules indirectly involved in the formation of CHD2OCHO and CH2DOCHO on the icy surfaces of interstellar dust grains. The relative deuteration of singly- and doubly-deuterated species is not correlated to the hot corino structure, but rather inform us about the chemical history of the cold protostellar envelope. The results suggest that the deuteration enhancement is inherited from their precursor species and that radical-radical addition on ice surfaces is the main formation reaction of CH3OCHO isotopologues.The detection of molecules containing three carbon atoms, C3-species, towa rds IRAS 16293B, such as propenal (C2H3CHO), propanal (C2H5CHO), methyl acetylene (CH3CCH), propene (C3H6), and trans-ethyl methyl ether (t-C2H5OCH3), made the study of their formation possible. We compared the observed abundances of these C3-species to those predicted by a three-phase chemical model, NAUTILUS, coupled to a 1D hydrodynamical model of an infalling protostellar envelope. The simulations could reproduce all the abundances of the observed C3-species, as well as those of other COMs, within one order of magnitude. Comparisons between simulations suggest that radical-radical additions and successive hydrogenation contribute equally to the formation of C2H3CHO and C2H5CHO. Also, a systematic over-production of molecules of the form C3Hx suggests that the chemical networks lack consumption channels for those species, which could be related to the chemistry of polycyclic aromatic hydrocarbons (PAHs).