Sigma and Pi Bonds quiz #1 Flashcards
Sigma and Pi Bonds quiz #1
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How many sigma (σ) bonds are present in a typical organic molecule containing single, double, and triple bonds? Each single bond contains one sigma bond; each double bond contains one sigma and one pi bond; each triple bond contains one sigma and two pi bonds. The total number of sigma bonds is the sum of all single bonds plus one sigma bond for each double and triple bond. How many carbon-oxygen sigma (σ) bonds are present in an organic molecule with both single and double carbon-oxygen bonds? Each single carbon-oxygen bond contains one sigma bond, and each double carbon-oxygen bond contains one sigma and one pi bond. Count the number of carbon-oxygen bonds and sum the sigma bonds accordingly. How many pi (π) bonds are present in a typical organic molecule containing single, double, and triple bonds? Each double bond contains one pi bond, and each triple bond contains two pi bonds. The total number of pi bonds is the sum of one for each double bond and two for each triple bond. How many pi bonds are present in acetylsalicylic acid? Count the number of double bonds in acetylsalicylic acid; each double bond contains one pi bond. The total number of pi bonds equals the number of double bonds present. Which type of covalent bond allows for free rotation about the bond axis? Sigma (σ) bonds allow for free rotation about the bond axis. Which orbitals can overlap to form a pi (π) bond? Pi bonds are formed by the sideways overlap of p orbitals. How many sigma (σ) bonds formed by s–sp2 overlap are present in a compound containing sp2-hybridized carbons? Each sp2-hybridized carbon forms sigma bonds with adjacent atoms through s–sp2 overlap. Count the number of such bonds in the compound. Which type of molecule contains only sigma (σ) bonds? Molecules containing only single bonds, such as alkanes, have only sigma bonds. What type of bond is present in ethene (C2H4)? Ethene contains a double bond between the two carbons, which consists of one sigma bond and one pi bond. What types of orbital overlap occur between two adjacent atoms to form a double bond? A double bond consists of one sigma bond formed by end-to-end overlap (usually s–sp2 or sp2–sp2) and one pi bond formed by sideways overlap of p orbitals. How are pi (π) bonds formed? Pi bonds are formed by the sideways overlap of parallel p orbitals. Which statement is correct regarding a pi (π) bond? A pi bond restricts rotation about the bond axis and is formed by sideways overlap of p orbitals. How many sigma and pi bonds are present in the molecule HCN (hydrogen cyanide)? HCN contains one single bond (H–C, one sigma) and one triple bond (C≡N, one sigma and two pi bonds), totaling two sigma bonds and two pi bonds. In how many sigma (σ) bonds does a typical atom in an organic molecule participate? The number of sigma bonds an atom participates in depends on its hybridization and bonding; for example, a carbon in methane participates in four sigma bonds. How many sigma (σ) and pi (π) bonds are present in a molecule of cumulene (H2C=C=C=CH2)? Cumulene contains three double bonds, each with one sigma and one pi bond, totaling four sigma bonds and three pi bonds. Which bond(s) allow(s) free rotation? Only sigma (σ) bonds allow free rotation; pi (π) bonds restrict rotation. Which compound contains both sigma and pi bonds: HCCl3, H2CO, H2S, or HBr? H2CO (formaldehyde) contains both sigma and pi bonds due to the carbon-oxygen double bond. How many sigma (σ) and pi (π) bonds are present in the molecule H2C=C=CH2? H2C=C=CH2 (cumulene) contains four sigma bonds and three pi bonds. What type(s) of orbital overlap occur in a molecule with double and triple bonds? Double bonds involve one sigma (end-to-end overlap) and one pi (sideways p orbital overlap); triple bonds involve one sigma and two pi overlaps. Which bonds are involved in the conjugated portion of a molecule? The conjugated portion of a molecule involves alternating single and double bonds, with pi bonds present in the double bonds. If a molecule has 10 sigma (σ) bonds, how can you determine the number of specified orbitals involved? Count the number of sigma bonds and identify the types of orbitals involved in each bond based on the hybridization of the atoms. How do you determine the number of sigma and pi bonds in a molecule? Count all single bonds as sigma bonds; each double bond adds one pi bond, and each triple bond adds two pi bonds. The total number of sigma and pi bonds is the sum based on the bonding pattern. What is required for a pi (π) bond to form between two atoms? A pi bond forms when two adjacent atoms have unhybridized p orbitals that can overlap sideways.
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