Simply Mechanisms 3c. Ethanol from the catalysed hydration of ethene HD

Top Tutors for all Subjects at all Levels here: https://spires.co/franklychemistry Find a mindmap here. http://franklychemistry.co.uk/simply_mechanisms/5_Simply_Mechanisms_ethene_hydration.pdf One in a series of videos looking at organic chemistry mechanisms. This one looks at the mechanism for the industrial preparation of ethanol by the catalysed hydration of ethane. The catalyst in phosphoric acid coated onto silica and the conditions are 300 Celsius at 60-70 atm. The H3PO4 molecule has three significantly polar O-H bonds. The C=C double bond is made up of a sigma and pi bond. All atoms attached to the C=C double bond in ethene lie on the same flat plane. The pair of electrons of the pi bond spend most of their time either above or below this plane. They are more exposed to incoming electrophiles and the pi bond is weaker than the sigma bond. This is presented as a 3-step mechanism. In the first step the pi bond breaks and one of the H-O- bonds of the acid breaks. The H-O bond breaks by way of heterolytic fission, meaning that both electrons of the bond go to the O atom of the :OPO3H- ion. This creates an :OSO3H- ion and a H+ electrophile. The pair of electrons of the pi bond are then used to form a bond with the H+ electrophile. The other carbon of the C=C bond will have lost the electron it contributed to form the original pi bond. It will then have a positive charge, explaining why the deficiency of the carbocations. In the next step a steam molecule uses one of its lone pairs to form a bond with the carbon bearing the +ve charge. In the third and final step the :OPO3H- ion removes a proton from the attached water molecule. This produces the organic product ethanol and regenerates the catalyst.