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Atoms of ethylene sp2-Hybridization of carbon Figure 1.24 Figure 1.25 sp-Hybridization of carbon Acetylene is a linear molecule Figure 1.29 Figure 1.28 O HO H VSEPR - Prediction of molecular geometry CO HO H O H CH3 COOH NCH3 OH CH2 Gibberellic Acid HO morphine HC C OOCNH2 sp3 - Tetrahedral geometry, 4 σ electron pairs, no π bonds sp2 - Trigonal planar, 3 σ electron pairs, 1 π bond sp - Linear geometry, 2 σ electron pairs, 2 π bonds O H3C OH H3C O CH2 O CH3 OH H3C CH3 H3C CH3 OH N CH3 HO O CH3 O OCH3 O CH3 O In each case the hybridization model is used to explain the molecular orbitals involved. The sigma (σ) bonds dictate molecular geometry and try to get as far away as possible from each other. CH3 OH CH3 1 Functional group classifications Chapter 2 - Alkanes Classification of hydrocarbons: aliphatic or aromatic Aliphatic (“fat”) Aromatic (“smell”) Alkanes, alkenes, Arenes - benzenes, alkynes polyaromatics Classifications are old but still useful for organizing families of compounds Simple Alkanes Structural Isomers C4H10 n-butane Methane (CH4) Ethane (C2H6) C4H10 isobutane Propane (C3H6) C5H12 C5H12 C5H12 n-pentane isopentane Neopentane Careful with drawing chains! CH3CHCH2CH3 CH3 CH3 CH3CHCH2CH3 CH3 CH3CH2CHCH3 CH3CH2CHCH3 CH3 CH3 CH2CH2CH3 CH3 All the same compound Table 2.2 – need to know names up to C12 2 IUPAC Rules and how to apply them Hexane (IUPAC); n-hexane (common) Rules: • Find the longest continuous carbon chain • Identify substituent groups attached to the chain Longest chain - hexane substituent - methyl • Number the chain so as to keep numbers small position on chain - 2 • Write the name in the following format: 2-methylhexane not 5-methylhexane Numerical location - [substituent(s)][parent alkane] 3,4-dimethylheptane e.g. 2,3-dimethylheptane Alkyl Substituents Replace -ane ending with -yl H C C H Primary (1o) C C C H Secondary (2o) CH3 CH3CH2CH2Propyl group CH3CH isopropyl group 1-methylethyl C C C C Tetriary (3o) CH3 H3C C CH3 t-Butyl group 1,1-dimethylethyl 3