Question

Among the following compounds which one has more than one type of hybridization of carbon (a) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\) (b) \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{C} \equiv \mathrm{CH}\) (c) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\)

Short answer

(a) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\) (b) \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{C} \equiv \mathrm{CH}\) (c) \(\mathrm{CH}_{3} \mathrm{CH}_{2}\mathrm{CH}\left(\mathrm{CH}_{3}\right)_{2}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2}\mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\) Answer: Both (b) \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{C} \equiv \mathrm{CH}\) and (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2}\mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\) have more than one type of hybridization of carbon atoms.

Step-by-step solution

Identify the hybridization of carbon atoms in compound (a)

In compound (a), \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}-\mathrm{CH}=\mathrm{CH}_{2}\), we see that there are four carbon atoms. The hybridizations are as follows: 1. The first carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to two hydrogen atoms and forms a double bond with the next carbon atom. 2. The second carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to the first and third carbon atoms and forms a double bond with the first carbon atom. 3. The third carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to the second and fourth carbon atoms and forms a double bond with the fourth carbon atom. 4. The fourth carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to two hydrogen atoms and forms a double bond with the third carbon atom. All four carbon atoms in compound (a) have the same hybridization, so this compound does not meet the criteria.

Identify the hybridization of carbon atoms in compound (b)

In compound (b), \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{C} \equiv \mathrm{CH}\), we see that there are three carbon atoms. The hybridizations are as follows: 1. The first carbon atom is \(\mathrm{sp}\) hybridized, as it forms a triple bond with the second carbon atom. 2. The second carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to the first and third carbon atoms and forms a single bond with the first carbon atom and a triple bond with the third carbon atom. 3. The third carbon atom is \(\mathrm{sp}\) hybridized, as it forms a triple bond with the second carbon atom. In compound (b), there are two types of hybridization, sp and sp2.

Identify the hybridization of carbon atoms in compound (d)

In compound (d), \(\mathrm{CH}_{3} \mathrm{CH}_{2}\mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\), we see that there are six carbon atoms. The hybridizations are as follows: 1. The first carbon atom is \(\mathrm{sp}^{3}\) hybridized, as it is bonded to three hydrogen atoms and forms a single bond with the second carbon atom. 2. The second carbon atom is \(\mathrm{sp}^{3}\) hybridized, as it is bonded to two hydrogen atoms and forms a single bond with the first and third carbon atoms. 3. The third carbon atom is \(\mathrm{sp}^{2}\) hybridized, as it is bonded to the second and fourth carbon atoms and forms a double bond with the fourth carbon atom. 4. The fourth carbon atom is \(\mathrm{sp}^{3}\) hybridized, as it is bonded to the third carbon atom and forms a single bond with two \(\mathrm{CH}_{3}\) groups. 5. The fifth and sixth carbon atoms are both \(\mathrm{sp}^{3}\) hybridized, as they are each bonded to three hydrogen atoms and form a single bond with the fourth carbon atom. In compound (d), there are two types of hybridization, sp2 and sp3.

Compare and conclude

Compound (b) and compound (d) both have more than one type of hybridization of carbon atoms. Therefore, the answer is both (b) \(\mathrm{HC} \equiv \mathrm{C}-\mathrm{C} \equiv \mathrm{CH}\) and (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2}\mathrm{COCH}\left(\mathrm{CH}_{3}\right)_{2}\).

Key concepts

sp3 hybridization

When we discuss the term sp³ hybridization, we are referring to a specific way that carbon atoms can organize their electron orbitals in organic compounds. In sp³ hybridization, a carbon atom's one s orbital and three p orbitals combine to form four equivalent sp³ hybrid orbitals. These newly formed orbitals are oriented in a tetrahedral shape, allowing for 109.5-degree bond angles, which optimizes the distance between electrons and minimizes repulsion.

This type of hybridization occurs in carbon atoms that are bonded to four other atoms, typically forming four sigma (\f\(\f\text{{\f\)sigma$\f}}}) bonds. A perfect example could be methane (CH₄), where the central carbon is surrounded tetrahedrally by four hydrogen atoms. When recognizing sp³ hybridization in molecules, looking for carbon atoms with four single bonds is a great start.

sp2 hybridization

Transitioning to sp² hybridization, it's crucial to understand that in this case, a carbon atom hybridizes one s orbital with two p orbitals, resulting in three sp² hybrid orbitals and one unhybridized p orbital. The hybrid orbitals lie on the same plane, 120-degrees apart, forming a planar triangular structure, while the unhybridized p orbital is perpendicular to this plane.

This arrangement gives rise to trigonal planar geometry around the carbon atom and allows it to form one double bond (comprising one sigma and one pi bond) along with two single bonds. Carbons involved in double bonds, like in ethene (C₂H₄), exhibit sp² hybridization. Identifying sp² hybridized carbons involves spotting carbon atoms with one double bond and two single bonds.

sp hybridization

The case of sp hybridization marks a scenario where the carbon atom combines one s orbital with just one p orbital, which crafts two identical sp hybrid orbitals aligned linearly and 180-degrees apart. This leaves two unhybridized p orbitals, which are perpendicular to each other as well as to the axis of the sp orbitals.

sp hybridization makes it possible for carbon to form two pi bonds and one sigma bond, and it is characteristic of carbon atoms involved in triple bonds, as in acetylene (C₂H₂). Such carbon atoms display a linear geometry. To recognize sp hybridization in a compound, one should look for carbon atoms with either a triple bond and a single bond or two double bonds.

Organic Chemistry

Organic chemistry is a fascinating and extensive branch of chemistry that focuses on the study of carbon-containing compounds. The versatility of carbon lies in its ability to form strong covalent bonds with other atoms, including another carbon, which allows the formation of long chains and rings that are the basis for the complexity of organic compounds.

Through the concepts of sp³, sp², and sp hybridization, we gain insight into how carbon atoms can form various molecular geometries and bonding schemes that ultimately determine the structure and properties of organic molecules. Thus, understanding the hybridization of carbon is fundamental to deciphering the diverse and intricate world of organic chemistry.