Hydroboration: Atom and Hydrogen Peroxide Essay

825 WordsJul 29, 20134 Pages
Hydroboration-Oxidation Purpose: The purpose of this lab is to analyze the results of hydroboration oxidation on a terminal alkene. Overall Reaction: Compound | MW | Density | BP | MSDS | 1-octene | 112.24 | .715 | 121 | Flammable, irritant | BH | 13.84 | .898 | 90 | Irritant | Tetrahydrofuran | 72.1 | .889 | 66 | Irritant | Hydrogen Peroxide | 34.0 | 1.135 | 152 | Corrosive, harmful | 1-octanol | 130.2 | .824 | 195 | Irritant | 2-octanol | 130.2 | .819 | 160 | Flammable | Discussion: Hydroboration-oxidation is a one step, conservative organic reaction that converts an alkene into a neutral alcohol by the addition of water across the double bond. This reaction is anti-Markovnikov, which leads to the hydroxyl…show more content…
Thus one of the hydrogen atoms from BH now bears a partial negative charge, and hence becomes more nucleophilic. The breaking pi bond transfers its free electrons to form a bond between the partial positively charged boron atom and negatively charged carbon while the electrons from the boron-hydrogen bond help create the bond between the partially positive carbon and negatively charged hydrogen. This whole process occurs two more times, resulting in a boron atom attached to three of the same alkyl groups along with its vacant 2p orbital. After hydroboration, treatment of the alkylborane with hydrogen peroxide in a base leads to the replacement of the borane atom with a hydroxyl group. Note that the stereochemistry is preserved. The first step is the deprotonation of hydrogen peroxide to give HOO because HOO is a better nucleophile and will speed up the rate of reaction for the next step. The nucleophilic HOO will then attack the trialkylborane compound and cause an alkyl shift where one of the alkyl groups bonds to the attacking oxygen. The hydroxyl group leaves at the same time this occurs, and this happens two more times. The end result is a trialkoxyborane compound. The trialkoxyborane is then attacked by a nucleophilic hydroxide and induces a negative charge on boron.

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