Question

Chapters 1-11 1. Carbenes are diradicals and can have a transient existence during many reaction (particularly with alkenes). Isopropylene, :C(CH3)2, is a example of a carbone. The two electrons can share the same orbital or occupy two different orbitals. Provide the expecte hybridization when the two electrons are spin unpaired. For when they Draw the atomic orbitals of each and identify the valence orbitals on the carbene. H Hoe & H₂O 2. Account for the fact that the following carbocation gives two alcohols on reaction wil water using an acid catalysis. Provide the mechanism for the reaction. Use cu to indicate electron flow. H OH Haac-C-oH HC. CH3 CH₃ 3. For each compound, sight along the C2-C3 bond and draw Newman projections of theCH least and most stable conformations. Which as most energy? The least? a. 2-methylbutane b. 2, 2, 3 - trimethylbutane 4. Draw the most stable form of these two isomers of inositol. Give the common IUPAC name for this important biomolecule. Ha HO OHHC Lacoste бн D inositol 5. Examine the reaction below. a. Is the product chiral? b. Assume the reaction takes place with nucleophilic attack preferentially on the si fc of the carbonyl group. Is the product chiral? Optically active? Explain. c. Draw curved arrows to indicate electron flow in each step. cria

Answer 1

Isopropylene carbene can exist in two states. One is singlet Isopropylene carbene in which unshared electrons are paired i. e they are present in same orbital. The central carbon in singlet carbene is sp² hybridized. There are three sp² hybrid orbitals. ​​Out of three hybrid orbitals, two are used in forming two single bonds with carbon atom of each methyl group. The third sp² hybrid orbital contains the unshared pair of electrons. The unhybridized p orbital is empty.

Second is Triplet Isopropylene carbene, in which unshared electrons are not paired i. e they are present in different orbitals. In triplet Isopropylene carbene, the central carbon atom is sp hybridized. The two sphybridized orbitals are used in forming two single bonds with carbon atoms of each methyl group. The two unhybridized orbital contain one unshared electron each.

CH₃ group . Empty 26 orbital Cunhybridized) Sp² orbital containing Lone pair of electrons Actually, hybrid orbitals have e Large lote and one small Hybridized orbital Llobe Sb? 0 Sp3 SINGLET ISOPROPYLENE representation of singlet Carbene - Empty 2p orbital - sp² hybridized Catom & 7 Simple for the sake of Simplicity we can draw / only brger lobe of hybrid ochital sp hybride unhybridized 26 orbital Sp hybridized (SP Carbon (40 Sp o 2umpaired electrons or - sb hy breidized Carbon Triplet Carbene (Isopropylene)

II -H+ H2CT 9 H+ H₂C = 4-¢-on CH3 CH3 CH3 CH3 Carbocation charged the positively positive is in conjugation we In this carbocation, the positively ch The double bond. conjugation with Charge of carbon gets dispersed over two atoms. Thus, the Carbocation is resonantica Stabilized. + سر ی ج ت - ال duz cn na cha on HTC - c-on En caz Thus, we get bath both resonance stabilization cho cha product due to of Carbocation.

The carbocation forms two alcohols due to resonance stabilization of carbocation. There are two resonantic structures of carbocation and alcohols corresponding each resonating structure are formed.