This invention provides an isolated compound having the structure: The invention also provides for a process for preparing 4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-4-ol, 1-(3,3-bis(3-(methylsulfonyl)phenyl)propyl)-4-(3-(methylsulfony l) phenyl)piperidone, 1,4-bis((3-(1 -propylpiperidin-4-yl)phenyl)sulfonyl)butane, (3R,4S)-4-(3-(methylsulfonyl)phenyl)-1-propylpiperidin-3-ol, 4-(3-(methylsulfonyl)phenyl)-l-propylpiperidine 1- oxide, 1-(2-methylpentyl)-4-(3-(methylsulfonyl)phenyl)piperidine, 4-(3-(methylsulfinyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin e, and 4-(3-(methylsulfonyl)phenyl)-1-propyl-1,2,3,6-tetrahydropyridin e. This invention also provides an impurity or a salt thereof for use, as a reference standard to detect trace amounts of the impurity in a pharmaceutical composition comprising pridopidine or a pharmaceutically acceptable salt thereof. This invention further provides a process for producing a pridopidine drug product comprising obtaining a pridopidine drug substance and mixing the pridopidine drug substance with suitable excipients so as to produce the pridopidine drug product. This invention also provides a process for producing a pridopidine drug product. This invention also provides a process of distributing a pridopidine drug product.Esta invención provee un compuesto aislado que tiene la siguiente estructura: (ver Fórmulas) o una sal del mismo. La invención también provee un proceso para preparar 4-(3-(metilsulfonil)fenil) -1-propilpiperidin-4-ol, 1-(3,3-bis(3-(metilsulfonil)fenil)propil) -4-(3-(metilsulfonil)fenil)piperidona,1,4-bis((3-(1-propilpiperid in-4-il)fenil)sulfonil)butano,(3R,4S)-4-(3-(metilsulfonil)fenil)- 1-propilpiperidin-3-ol,1-óxido de 4-(3-(metilsulfonil) fenil)-1-propilpiperidina,1-(2-metilpentil)-4-(3-(metilsulfonil)f enil)piperidina,4-(3-(metilsulfinil)fenil)-1-propil-1,2,3,6-tetra hidropiridina, y 4-(3-(metilsulfonil) fenil)-1-propil-1,2,3,6-tetr ahidropiridina. Esta invención también provee una impureza o una sal de
