122Ch2 alkane lecture

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Chemistry 122 Introductory Organic Chemistry Fall Quarter 2015 Dr Thomas H Schultz What is Organic chemistry? What is Organic chemistry? The study of carbon and its compounds What is Organic chemistry? The study of carbon and its compounds First we will talk about compounds just containing carbon and hydrogen, these compounds are called hydrocarbons What is Organic chemistry? The study of carbon and its compounds First we will concentrate on compounds just containing carbon and hydrogen, these compounds are called hydrocarbons Hydrocarbon Classification Hydrocarbons Alkanes Cycloalkanes Alkenes Cycloalkenes Alkynes Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H? Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H8 d C4H? Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 C Draw Lewis Structures c C3H8 d C4H10 Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 C Draw Lewis Structures H C H H H CH4 c C3H8 d C4H10 Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H8 C Draw Lewis Structures H C H H H H CH4 H H C C H H H C2 H6 d C4H10 Cyclopropane • Large ring strain due to angle compression • Very reactive, weak bonds => Cyclopropane (2) Torsional strain because of eclipsed hydrogens Cyclobutane • Angle strain due to compression • Torsional strain partially relieved by ring puckering => Cyclopentane • If planar, angles would be 108°, but all hydrogens would be eclipsed • Puckered conformer reduces torsional strain Cyclohexane • Combustion data shows it’s unstrained • Angles would be 120°, if planar • The chair conformer has 109.5° bond angles and all hydrogen's are staggered • No angle strain and no torsional strain Chair Conformer Boat Conformer Conformational Energy Axial and Equatorial Positions Monosubstituted Cyclohexanes 1,3-Diaxial Interactions Disubstituted Cyclohexanes Cis-Trans Isomers Bonds that are cis, alternate axial-equatorial around the ring CH3 CH3 One axial, one equatorial => Bulky Groups • Groups like t-butyl cause a large energy difference between the axial and equatoria l conformer • Most stable conformer puts t-butyl equatorial regardless of other substituents => End of Chapter [...]...1 Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H8 d C4H10 C Draw Lewis Structures H C H H H H CH4 H H C C H H H C2 H6 H H H H C C C H H H H C3H8 1 Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B... an alkane containing five carbons (C5H12)? Isomer Strategy – Draw Lewis possible different length chains of carbons atoms connected with a covalent bond Isomerism Constitutional Isomers (Structural Isomers) are different compounds of the same formula The different structures from the previous slide for the formula C 4H10 is an example of Constitutional isomers How many isomers are there of an alkane. .. H H C C C H H H H Step #1, count the number of carbons and write down the memorized Latin name for that number (next slide) Step #2, since this structure fits the alkane general formula, use the “ane” suffix propane Three carbon Latin root Alkane suffix Latin Hydrocarbon Roots Latin Hydrocarbon Roots Number of Latin Carbons Root Number of Latin Carbons Root Examples H H H H H C C C H C H H H H n-butane... hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H8 d C4H10 C Draw Lewis Structures H C H H H H CH4 H H C C H H H C2 H6 D Polarity? Polar or nonpolar? H H H H C C C H H H H C3H8 1 Alkanes (saturated) hydrocarbons, or aliphatic hydrocarbons) A General formula of CnH2n+2 B Examples a CH4 b C2H6 c C3H8 d C4H10 C Draw Lewis Structures H C H H H H CH4 H H C C H H H C2 H6 H H H H C C... atoms How many primary, secondary, and tertiary carbons in the two different structures of C4H10 H H C H H H H C C C H H H H Isobutane C4H10 Primary carbon = 3 Secondary carbon = 0 Tertiary carbon = 1 1 Alkanes (Continued) F There are two different structures for C4H 10 called isomers, because they contain different types of carbon Structure 1 H H H H H C C C C H H H H H Butane, C4H10 H Structure 2 H... Nomenclature (IUPAC) •Find the longest continuous chain of carbon atoms •Use a Latin root corresponding to the number of carbons in the longest chain of carbons •Follow the root with the suffix of “ane” for alkanes •Carbon atoms not included in the chain are named as substituents preceding the root name with Latin root followed by “yl” suffix •Number the carbons, starting closest to the first branch •Name
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