What orbitals are used to form the carbon-carbon σbond...

What orbitals are used to form the carbon-carbon $\sigma$ bond between the highlighted carbons? a. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}$ b. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}$ c. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{C}=\mathrm{CH}_{2}$ d. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{3}$ e. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{3}$ f. $\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CH}_{2}$ g. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}_{3}$ h. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{2} \mathrm{CH}_{3}$ i. $\mathrm{CH}_{2}=\mathrm{CHC} \equiv \mathrm{CH}$

What orbitals are used to form the carbon-carbon $\sigma$ bond between the highlighted carbons?
a. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}$
b. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{3}$
c. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{C}=\mathrm{CH}_{2}$
d. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{3}$
e. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{3}$
f. $\mathrm{CH}_{2}=\mathrm{CHCH}=\mathrm{CH}_{2}$
g. $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{CH}_{3}$
h. $\mathrm{CH}_{3} \mathrm{C} \equiv \mathrm{CCH}_{2} \mathrm{CH}_{3}$
i. $\mathrm{CH}_{2}=\mathrm{CHC} \equiv \mathrm{CH}$

Key Concepts

Orbital Overlap

Orbital overlap is the process by which electrons in atomic orbitals on adjacent atoms interact and combine to form molecular orbitals. In the case of sigma bonds, the overlapping orbitals are aligned along the internuclear axis, ensuring maximum electron density between the nuclei. The nature of this overlap—whether involving sp, sp2, or sp3 orbitals—determines not only the strength of the bond but also the overall molecular geometry.

Molecular Geometry

Molecular geometry stems from the hybridization state of atoms and dictates the spatial arrangement of bonds around an atom. This geometric arrangement impacts how orbitals align and overlap to form both sigma and pi bonds. For instance, an sp2-hybridized carbon atom has a trigonal planar arrangement that optimizes the overlap for sigma bonding in a double bond, while an sp-hybridized carbon is linear to best facilitate sigma bond formation in a triple bond.

Hybridization

Hybridization describes the mixing of atomic orbitals to form new, directed orbitals that participate in bond formation. In carbon atoms, the type of hybridization (sp3, sp2, sp) determines the geometry and orientation of the resulting orbitals, which in turn affects how sigma bonds are formed. For example, sp2 hybridization typically results in a planar structure that directs one of the hybrid orbitals for sigma bonding, while the remaining unhybridized p orbitals form pi bonds.

Sigma Bond Formation

Sigma bonds are formed by the head-on (axial) overlap of atomic orbitals along the line connecting the nuclei. This direct overlap, whether between sp, sp2, or sp3 orbitals, creates a strong bond that is fundamental to the structure of organic molecules. In multiple bonds, the sigma bond represents the primary strong linkage between the two carbon atoms, with additional bonding supplied by pi bonds from sideways orbital overlap.

Transcript

00:05 This question asks us to figure out which orbitals are used to form a sigma bond between the highlighted carbons on each compound.

00:13 So the first thing i want to talk about is orbitals.

00:16 So we have several hybrid orbitals is what we're going to be talking about.

00:21 We have sp, sp2, and sp3.

00:25 So a general rule of thumb, a really easy way to figure out what orbital we're in is if you have a carbon with two things bonded.

00:35 To it.

00:35 So two different bonds.

00:37 These could be two double bonds.

00:40 It could be a single bond and a triple bonds.

00:41 It could be any number of combinations of that.

00:45 That is going to be an sp.

00:47 An sp2 will be a carbon with three different bonds on it, probably a hydrogen on one of those.

00:54 It could be two hydrogens.

00:58 It could be two carbons on these.

01:00 Either way, we'll have three bonds.

01:03 Usually that means one triple bond or one double bond and then sp3 carbon it has four bonds on it so it could be all h's it could be all carbons but four bonds so that's how we're going to figure out which orbital each of these are in so on a um the one on the left has a carbon a hydrogen and then a double bond on it so that is three bonds so that is sp2.

01:33 And then the other one here also has a carbon, a hydrogen, and that double bond.

01:40 So it's also sp2.

01:43 B, the first carbon has a double bond, a hydrogen, and another carbon.

01:48 So that is an sp2.

01:51 And then the second carbon in this problem has three hydrogens and a carbon.

01:57 So that will be sp3, because it has four bonds.

02:03 On c, this first carbon has two different ones.

02:07 It has two double bonds around it, but that's two different things bonded to it.

02:12 So that'll be sp.

02:13 And then the one on the end has two hydrogens and that double bond.

02:17 So that's three things bonded to it.

02:19 So that's an sp2.

02:22 D, the first one has a triple bond on one side and a carbon on the other...

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