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Zorluk: OrtaTetrahedral Carbon, Bonding, and Hybridization

What is the total number of sigma (σ\sigma) bonds in a single molecule of prop-2-enal (acrolein, CH2=CH−CHO\text{CH}_2=\text{CH}-\text{CHO})?

Cevap: 7 / seven / 7 sigma bonds / 7 sigma

Cevap

7
Expanding prop-2-enal (CH2=CH−CHO\text{CH}_2=\text{CH}-\text{CHO}) reveals four C−H\text{C}-\text{H} single bonds, one C−C\text{C}-\text{C} single bond, one C=C\text{C}=\text{C} double bond (composed of one σ\sigma and one π\pi bond), and one C=O\text{C}=\text{O} double bond (composed of one σ\sigma and one π\pi bond). Summing all head-on orbital overlaps yields a total of 7 sigma (σ\sigma) bonds.

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1
Draw the expanded structural formula of prop-2-enal.
The expanded formula showing all individual atoms and bonds is H2C=CH−C(=O)H\text{H}_2\text{C}=\text{CH}-\text{C}(=\text{O})\text{H}.
Expanding the structural formula ensures that all implicit single bonds, double bonds, and hydrogen attachments are explicitly visible for counting.
2
Count all carbon-hydrogen (C−H\text{C}-\text{H}) single sigma bonds.
There are 2 C−H\text{C}-\text{H} bonds on the terminal alkene carbon, 1 C−H\text{C}-\text{H} bond on the central alkene carbon, and 1 C−H\text{C}-\text{H} bond on the aldehyde carbon, giving a total of 4 C−H\text{C}-\text{H} σ\sigma bonds.
Every single covalent bond formed with hydrogen involves head-on sp2−ssp^2-s orbital overlap and constitutes one σ\sigma bond.
3
Count the sigma bonds among the carbon-carbon and carbon-oxygen links.
The C=C\text{C}=\text{C} double bond contains 1 σ\sigma bond, the C−C\text{C}-\text{C} single bond contains 1 σ\sigma bond, and the C=O\text{C}=\text{O} double bond contains 1 σ\sigma bond, giving 3 heavy-atom σ\sigma bonds.
Every covalent bond—whether single, double, or triple—contains exactly one σ\sigma bond resulting from axial head-on orbital overlap.
4
Sum the total number of sigma bonds.
4 (C-H \sigma bonds)+3 (C-C and C-O \sigma bonds)=7 \sigma bonds4\text{ (C-H \sigma\ bonds)} + 3\text{ (C-C and C-O \sigma\ bonds)} = 7\text{ \sigma\ bonds}.
Adding all localized head-on orbital overlaps gives the total count of sigma bonds in the molecule.

Anahtar Kavram

Determination of sigma (σ\sigma) and pi (π\pi) bond counts in organic structures
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Konular

Tetrahedral Carbon, Bonding, and Hybridization

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