A method comprising: 1) providing A') an olefinic nitrile comprising a cyanide impurity of formula X'-C≡N, where X' is hydrogen, sodium, or potassium, 2) removing all or a portion of the cyanide impurity from A') the olefinic nitrile, thereby producing A) a purified olefinic nitrile; wherein step 2) comprises one or more of combining A') the olefinic nitrile and an elemental metal selected from the group consisting of copper, iron, silver, or nickel; or combining A') the olefinic nitrile and an adsorbent selected from the group consisting of activated carbon and molecular sieves; or combining A') the olefinic nitrile to a metal selected from the group consisting of copper, iron, silver, or nickel, or the oxides of these metal; and thereafter combining the product and an absorbent to form A) the purified olefinic nitrile; and 3) combining, at a temperature of 20 °C to 150 °C, starting materials comprising A) the purified olefinic nitrile; B) the hydridosilane, where the hydridosilane has formula R1 x HSiX (3-x) , where subscript x is 0, 1, or 2; each R 1 is an independently selected monovalent hydrocarbon group of 1 to 18 carbon atoms, and each X is independently selected from the group consisting of a halogen atom and an alkoxy group of formula OR 1 ; and C) a platinum hydrosilylation reaction catalyst in an amount sufficient to provide 5 ppm to < 200 ppm Pt based on combined weights of starting materials A), B), and C). 1) providing A') an olefinic nitrile comprising a cyanide impurity of formula X'-C≡N, where X' is hydrogen, sodium, or potassium, 2) removing all or a portion of the cyanide impurity from A') the olefinic nitrile, thereby producing A) a purified olefinic nitrile; wherein step 2) comprises one or more of combining A') the olefinic nitrile and an elemental metal selected from the group consisting of copper, iron, silver, or nickel; or combining A') the olefinic nitrile and an adsorbent selected from the group consisting of activated carbon and molecular sieves; or combining A') the olefinic nitrile to a metal selected from the group consisting of copper, iron, silver, or nickel, or the oxides of these metal; and thereafter combining the product and an absorbent to form A) the purified olefinic nitrile; and combining A') the olefinic nitrile and an elemental metal selected from the group consisting of copper, iron, silver, or nickel; or combining A') the olefinic nitrile and an adsorbent selected from the group consisting of activated carbon and molecular sieves; or combining A') the olefinic nitrile to a metal selected from the group consisting of copper, iron, silver, or nickel, or the oxides of these metal; and thereafter combining the product and an absorbent to form A) the purified olefinic nitrile; and 3) combining, at a temperature of 20 °C to 150 °C, starting materials comprising A) the purified olefinic nitrile; B) the hydridosilane, where the hydridosilane has formula R1 x HSiX (3-x) , where subscript x is 0, 1, or 2; each R 1 is an independently selected monovalent hydrocarbon group of 1 to 18 carbon atoms, and each X is independently selected from the group consisting of a halogen atom and an alkoxy group of formula OR 1 ; and C) a platinum hydrosilylation reaction catalyst in an amount sufficient to provide 5 ppm to < 200 ppm Pt based on combined weights of starting materials A), B), and C). A) the purified olefinic nitrile; B) the hydridosilane, where the hydridosilane has formula R1 x HSiX (3-x) , where subscript x is 0, 1, or 2; each R 1 is an independently selected monovalent hydrocarbon group of 1 to 18 carbon atoms, and each X is independently selected from the group consisting of a halogen atom and an alkoxy group of formula OR 1 ; and C) a platinum hydrosilylation reaction catalyst in an amount sufficient to provide 5 ppm to < 200 ppm Pt based on combined weights of starting materials A), B), and C). <EOS>