This dataset contains the information (both experimental and computational) that was the basis of the paper: "The methyl torsion in unsaturated compounds" which was published in ACS Omega (2019). The dataset consists of a README file ("README_Zachariou_Methyl-torsion_dataset.txt " which has a detailed description of the data and four directories: "A-Experimental_INS_spectra", "B-CASTEP", "C-Gaussian" "D-Calculated_INS_spectra" that hold the data. The contents of "A-Experimental_INS_spectra" were recorded with TOSCA at ISIS (Chilton, UK), those of "B-CASTEP" were generated using the CASTEP computational package (version 17.21.), those of "C-Gaussian" were generated using the Gaussian 09W computational package (version 9.5) and those of "D-Calculated_INS_spectra" were generated using either of the programs ACLIMAX or AbINS (the latter is available within Mantid: https://www.mantidproject.org/Main_Page ).EP/R026939/1, EP/R026815/1, EP/R026645/1, EP/R027129/1 and EP/M013219/1