Aldehyde $B$ reacts with $C{H}_{3}MgBr$ to give isomeric products of molecular formula $C_4{H}_{10}O,$ Figure $4.$

Figure $4$

Discuss the mechanism for the reaction shown in Figure $4.$

Draw the structure of the products generated by the reaction in Figure $4.$ Include a brief explanation of the stereochemistry of the products in your answer.

Identify the $Re$ and $Si$ faces of aldehyde B$.$ Justify your answer in each case.

Identify the product that results from attack at the $Re$ face of aldehyde $B.$

Identify the product that results from attack at the $Si$ face of aldehyde $B.$