Question

Answer the following questions using the structure provided h) What is the C1-C2-N3 bond angle in ethanamine? ____ i) What is the H-Cl-H bond angle? ____ j) What is the bond angle between any two hydrogen on C3? ____ k) How many electrons are involved in sigma bonds ? ____ l) How many electrons are involved in pi bonds? ___ m) Mark as True or False: The C1-C2 bond is: able to freely rotate ___ shorter than the C2-N3 bond ____ an sp^2-sp^2 bond___ n) Draw an MO bonding picture for proponent independently showing the sigma-framework and the pi-framework. Which of the following has the MOST and LEAST amount of ring strain (CIRCLE)? Assign R or S stereochemistry to the chiral centers in the following Fischer Projection.

Answer 1

Answer to h) The aminoethene molecule is not planar because of the fact that the N-atom has a pyramidal geometry. However, the rigidity of the sp² hybridised C-atom will have major contribution to the C-C-N angle and prevent it from prevent high deviations. Hence, the C-C-N bond angle will be slightly more than 120^o (approx. 125^o).

Answer to i) Since C atom is sp² hybridised, the H-C-H angle will be 120^o.

Answer to j) the N-atom adopts a pyramidal geometry by undergoing hybridisation similar to sp³. Hence the H-N-H angle will be 109.5 ^o.

Answer to k) A sigma bond is formed by sharing of two electrons, one from each atom, along the bond axis. Let us consider the sigma bonds in this molecule.

There are two sp² hybridised C-atoms contributing total of 6 electrons towards sigma bond, five s orbitals of hydrogen atoms contributing total of 5 electrons towards sigma bond and a sp³ hybridised N-atom contributing total of 3 electrons towards sigma bond (note remaining two electrons do not take part in sigma bond and stay as lone pair). This totals to 14 electrons involved in seven sigma bonds.