Calicheamicin is an antitumor compound produced by a microorganism
isolated in Texas soil. Below is the enediyne core of calicheamicin, which is
responsible for its antitumor activity.
(a) Mark the hybridization state of each carbon. Ignore the –R groups.
(b) What are the ideal bond angles for these carbons?
To determine the hybridization state of each carbon in the enediyne core of calicheamicin, we need to count the number of sigma bonds and lone pairs of electrons around each carbon atom. The hybridization state is determined by the number of areas of electron density around the carbon.
(a) Let's mark the hybridization state of each carbon in the enediyne core of calicheamicin:
In the enediyne core, we have two carbons bonded to each other with a triple bond and two additional carbon atoms bonded to each of them. The hybridization states are as follows:
- The carbon atoms connected by the triple bond in the middle are sp hybridized. This is because they each form two sigma bonds (one with each other) and have no lone pairs of electrons.
- The two terminal carbon atoms are sp² hybridized. This is because they each form three sigma bonds (one with the middle carbon and two with hydrogen atoms) and have no lone pairs of electrons.
(b) The ideal bond angles for each carbon in the enediyne core can be determined based on their hybridization states:
- The sp-hybridized carbon atoms have a linear geometry, meaning the bond angle is 180 degrees.
- The sp²-hybridized carbon atoms have a trigonal planar geometry, meaning the bond angle is approximately 120 degrees.
So, in summary:
(a) The hybridization states of the carbons in the enediyne core are:
- The carbon atoms connected by the triple bond: sp hybridized
- The two terminal carbon atoms: sp² hybridized
(b) The ideal bond angles for each carbon are:
- The carbon atoms connected by the triple bond: 180 degrees
- The two terminal carbon atoms: approximately 120 degrees