Chem 102 1st Edition Lecture 3 Outline of Last Lecture I. Chapter 12 : 1.1 – 1.6: Organic and Inorganic Compounds, Bonding Characteristics of theCarbon atom, Hydrocarbons and Hydrocarbon Derivatives, Alkanes : Acyclic Saturated Hydrocarbons, Structural Formulas, Alkane IsomerismOutline of Current Lecture II. 1.7 - Conformations of AlkanesIII. 1.8 - IUPAC Nomenclature of AlkanesIV. 1.9 - Line-Angle Structural Formulas for AlkanesV. 1.10 - Classification of Carbon AtomsVI. 1.11 - Branched-Chain Alkyl GroupsVII. 1.12 - CycloalkanesCurrent Lecture1.7 - Conformations of Alkanes• Conformation: The specific three dimensional spatial arrangement of atoms in an organic molecule at agiven instant • Different conformational structures result from C-C single bond rotation, but no breaking of bonds takes place. • Different structural isomers result from different connectivity of atoms, which requires breaking and making of bonds in the same molecule.1.8 - IUPAC Nomenclature of Alkanes• Systematic approach for naming alkanes was introduced by the International Union of Pure and Applied Chemistry (IUPAC), and the rules are being updated periodically. • The rules are applied to both types of alkanes: – Straight chain (continuous) alkanes – Branched chain (divided / substituted) alkanes – Substituent: an atom or group of atoms attached to a chain (or ring) of carbon atoms.– Alkyl group: the group of atoms that would be obtained by removing a hydrogen atom from an alkaneIUPAC Rules for Naming Branched-Chain AlkanesRule 1: Identify the longest continuous carbon chain and name that chain as the parentRule 2: Number the carbon atoms in the parent chain in such a way so that to give the lowest possible number for a substituent (alkyl group). Rule 3: If only one substituent present, name and locate it by number; then, prefix the number and name to that of the parent carbon chain. Rule 4: If two or more of the same kind of alkyl group are present in a molecule, indicate the number with a Greek numerical prefix (di-, tri-, tetra-, penta-, and so forth). In addition, a number specifying the location of each identical group must be included. These position numbers, separated by commas, precede the numerical prefix. Numbers are separated from words by hyphens.IUPAC Rules for Naming Branched-Chain AlkanesRule 5: When two kinds of alkyl groups are present on the same carbon chain, number each group separately, and list the names of the alkyl groups in alphabetical order. Rule 6: Follow IUPAC punctuation rules: 1. Separate numbers from each other by commas. 2. Separate numbers from letters by hyphens. 3. Do not add a hyphen or a space between the lastnamed substituent and the name of the parent alkane.1.9 - Line-Angle Structural Formulas for Alkanes• Line-angle (Bond-Angle) structural formula: – A structural representation in which a line represents a carbon– carbon bond. – A carbon atom is understood to be present at every point where two lines meet (at the intersection) and at the ends of lines.• Structures of branched-chain alkanes designated using line-angle structural formulas.1.10 - Classification of Carbon AtomsBased on the skeletal structure of the C-atom in a hydrocarbon chain, each C-atom can be classified as follows: – Primary: If bonded to only one C- atom – Secondary: If bonded to 2 other C-atoms – Tertiary: If bonded to 3 other C- atoms – Quaternary: If bonded to 4 other C- atoms 1.11 - Branched-Chain Alkyl Groups• Continuous chain alkyl groups: The simplest type of alkyl group with continuous chain of carbon atoms.• Branched-chain alkyl groups: Alkyl groups are added to the continuous parent chain of carbon atoms (Alkanes with branched-chain alkyl groups).IUPAC naming of branched alkyl groups – A hyphen always follows the designations secondary and tertiary but no hyphen is used with prefix iso. – Examples: secondary-butyl tertiary-butyl isobutylIUPAC rules in naming branched chain alkyl groupsRule 1: The longest continuous carbon chain that begins at the point of attachment of the alkyl group becomes the base name. Rule 2: The base chain is numbered at the point of attachment. Rule 3: Substituents on the base chain are listed in alphabetical order, using numerical prefixes when necessary, and substituent locations are designated using numbers.1.12 - Cycloalkanes• Cycloalkanes are alkanes that contain a ring of three or more carbons. • General Formula of Cycloalkane: