Important Concepts Examples of each are T9yCeakgneemencaturoe:Denaeatomtat Q82 2. 3. Bond ang Toslonalstainrinablytoadoptstaggered ossepoabee ation of an 4 Important Concepts Important Concepts ond ange strain in small molecules 9 it 1.3 nes other than Ring Strain ins nall Cycloa 1. 2.BcyiRingSystom:May 4 Important Concepts 66 Sex hormones are divided into three types: Male sex hormones (androgens), female sex hormones (estrogens), and pregnancy hormones (progestins). Examples of each are •Testosterone Produced by testes. Responsible for masculine characteristics. •Estradiol Responsible for secondary female characteristics and participates in regulation of menstrual cycle. •Progesterone: Responsible for preparing the uterus for the implantation of an egg. 4 Important Concepts 1. Cycloalkane Nomenclature: Derived from that of the straight chain alkanes. 2. Cycloalkanes exist as two isomers unless they are 1,1-disubstituted. Cis: both substituents on the same face of the molecule; Trans: substituents on opposite faces. These are examples of stereoisomers. 3. Cycloalkanes may be strained. • Bond angle strain: Distortion about tetrahedral carbon. • Torsional strain: Inability to adopt staggered conformations. • Transannular strain: Steric repulsion between atoms across a ring. 4 Important Concepts 4. Bond angle strain in small molecules: Formation of bent bonds. 5. Strain in cycloalkanes other than cyclopropane: Deviations from planarity. 6. Ring Strain in Small Cycloalkanes: Reactions result in ring opening. 7. Deviations from Planarity: Lead to conformationally mobile structures. For cyclohexane, chair, boat, and twist-boat conformations lead to an almost strain-free structure. 8. Chair Cyclohexane: Axial and equatorial hydrogens are rapidly interconverted at room temperature by chair-chair interconversion (activation energy: 10.8 kcal/mol) 4 Important Concepts 9. Monosubstituted Cyclohexanes: Chair-chair interconversion ΔGo is substituent dependent. Axial substituents exhibit 1,3-diaxial interactions. 10. More Highly Substituted Cyclohexanes: Substitutent effects are often additive. Bulkiest substituents most likely to be equatorial.\ 11. Completely Strain Free Cycloalkanes: Adopt an all-anti conformation and lack transannular interactions. 12. Bicyclic Ring Systems: May be fused or bridged. Fusion may be cis or trans. 13. Natural Products: Classified by structure, physiological activity, taxonomy, and biochemical origin. 4 Important Concepts 14. Terpenes: Made of of 5 carbon isoprene units. 15. Steroids: Three angularly fused cyclohexanes (A,B,C rings) attached to a cyclopentane D ring. • Beta substituents: above the molecular plane. • Alpha substituents: below the molecular plane. 16. Sex Hormones: Steroids controlling physiological functions, including fertility