Question

 

Draw a Lewis structure for a compound with molecular formula C₄H₁₁N in which three of the carbon atoms are bonded to the nitrogen atom. What is the geometry of the nitrogen atom in this compound? Does this compound exhibit a molecular dipole moment? If so, indicate the direction of the dipole moment.

Answer 1

Concepts and reason

The nitrogen-containing organic compounds are known as amines. They are basic in nature, and lone pairs of electrons are present on the nitrogen atom. The general formula of amines is . Hence, they can be called as derivatives of ammonia. Amines can be classified as primary, secondary, or tertiary depending upon how many alkyl groups are attached to the nitrogen atom in amines.

The geometry of any molecule is basically the three-dimensional arrangement of atoms in the molecule. The geometry of any molecule can be determined from its Lewis structure. The molecular geometry depends upon both bonding electron pairs and non-bonding electron pairs.

The dipole moment measures the polarity of a bond within a molecule. A polar molecule has an unequal distribution of electrons. The dipole moment in any molecule is represented by the cross-base arrow where the cross represents the positive charge and the arrow represents the negative charge.

Fundamentals

When one of the hydrogen atoms in ammonia is replaced by an alkyl group, then the amine is known as a primary amine or a amine. The general formula of the primary amine is . Thus, nitrogen is attached to only one carbon atom.

When two of the hydrogen atoms in ammonia is replaced by an alkyl group, then the amine is known as a secondary amine or a amine. The general formula of secondary amine is . Thus, nitrogen is attached to two carbon atoms.

When all the hydrogen atoms in ammonia are replaced by an alkyl group, then the amine is known as a tertiary amine or a amine. The general formula of the tertiary amine is . Thus, nitrogen is attached to only three carbon atoms.

The general rules to determine the geometry of any molecule given by VSEPR theory is follows:

1. The Lewis structure is drawn.

2. The number of bondpairs and lone pairs on the central atom is identified.

3. Identify the total number of electron groups.

4. Predict the geometry on the basis of electron groups in the molecule.

The general rule to predict the dipole moment of any molecule is to check the presence of lone pairs of an electron on it. A molecule having lone pairs of electrons on the central atom is a polar molecule and has a dipole moment. Another criterion to predict the dipole moment is to check the electronegativities of the elements present in the molecule.

The valence number of electrons in nitrogen is five. It is bonded to three carbon atoms. Two lone pairs of electrons must be present on it if there is no formal charge on nitrogen.

The Lewis structure of the compound with molecular formula is shown below:

The Lewis structure of the compound is shown below:

The number of bond pairs is three, and the number of lone pairs is one. Thus, the total number of electron groups is four.

The geometry of the compound is trigonal planar. The Lewis structure should be drawn as follows:

Amines are polar compounds and have a dipole moment. The electronegativity and the electron-donating properties of both nitrogen and carbon due to which there are two poles observed in the molecule.

The direction of the dipole moment is shown below:

Ans:

The Lewis structure of the compound with a molecular formula such that three carbon atoms are bonded to the nitrogen atom is shown below:

The geometry of the nitrogen atom in the compound with a molecular formula such that three carbon atoms are bonded to the nitrogen atom is trigonal pyramidal.

The compound of molecular formula has a dipole moment. The direction of the dipole moment is shown below: