The presence of an unshared pair of electrons on nitrogen causes the angle C–N–E (where E is C or H) to be less than 109.5°; for example, it is 108° in trimethylamine.
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The presence of an unshared pair of electrons on nitrogen causes the angle C–N–E (where E is C or H) to be less than 109.5°; for example, it is 108° in trimethylamine.
In amines like trimethylamine (N(CH₃)₃), the C-N-E angle (where E represents an electron pair or another substituent) is less than the ideal tetrahedral angle of 109.5° due to the presence of a lone pair on nitrogen. The lone pair exerts greater repulsion than a bonded pair, causing the other three bonding pairs to compress slightly. This lone pair-bond pair repulsion results in a smaller C-N-E angle, leading to a distorted trigonal pyramidal geometry. As a result, the actual angle in trimethylamine is approximately 107.3°, reflecting the influence of the lone pair on the molecular geometry.