Lecture 4A Saturated Hydrocarbons

• Formula or model

  Lewis Structure - Shows all bonds, all atoms, and all nonbonding e-
• Formula or model

  Structural Formula - same as lewis structure except nonbonding e- are not shown
• Formula or model

  Condensed structural formula - bonds are collapsed so relative positions of atoms are group together
• Formula or model

  Bond line structure - only bonds and functional groups are shown and each endpoint and bend represent carbon atoms
• Formula or model

  Ball-and-stick model - Atoms are shown as balls and bonds as sticks and the shape is shown at the central atom
• Formula or model

  Space-filling model - bonds are omitted and the size of atoms are emphasized
• Hydrocarbons - are compounds that are composed entirely of carbon and hydrogen atoms bonded to each other by covalent bonds
• Fossil fuels - natural gas, petroleum, and coal are the principal sources of hydrocarbons
• Two categories of hydrocarbons

  1. aliphatic (do not contain benzene ring)
  2. aromatic (contain a benzene ring)
• Classes of Hydrocarbons

  A) Aliphatic

  B) Aromatic

  C) Alkanes

  D) Alkenes

  E) Alkynes

  F) Cycloalkanes

  G) Cycloalkenes

  
• Alkanes - compounds with C-C single bonds and C-H bonds (no functional groups)
• Alkanes are also known as paraffins or saturated hydrocarbons
• alkanes - straight or branched-chain hydrocarbons with only single covalent bonds between the carbon atoms
• Homologous series - when each member of a series differs from the next member by a CH2 group
• Members of a homologous series are similar in structure, but have a regular difference in formula
• CnH2n+2 -> general formula for open chain alkanes
• Alkanes contain saturated carbon atoms that have four sigma bonds
• Sigma bonds - are linear bonds formed by a pair of electrons in overlapping atomic orbitals
• carbon has the ability to form two, three, or four sigma bonds because of its ability to hybridize its valence shell electron
• sigma bond -> a C-C and C-H single bond result from the overlap of sp3 orbitals
• A sigma bond exists if the electron cloud formed by the pair of bonding electrons lies on a straight line drawn between the nuclei of the bonded atoms
• Isomerism - the phenomenon of two or more compounds having the same molecular formula but different structural arrangements of their atoms
• name

  A) butane

  
• name

  A) isobutane

  
• isomers - compounds that have the same molecular formula, but different structural formulas
• constitutional isomers - isomers that differ in how their atoms are arranged in chains
• alkyl groups have the general formula CnH2n+1
• The letter R is often used in formulas to mean any of the many possible alkyl groups
• identify

  A) primary

  B) primary

  C) secondary

  D) tertiary

  E) primary

  
• carbon-carbon bonds are non-polar since they are between like atoms
• carbon-hydrogen bonds are only slightly polar
• the bonds is an alkane are symmetrically directed toward the corners of a tetrahedron
• due to their low polarity, alkane molecules have relatively low boiling points compared with other organic compounds of similar molar mass
• IUPAC meaning - International Union of Pure and Applied Chemistry
• Name

  A) 4-ethyl-5,6-dimethyldecane

  
• Cyclic molecules - commonly encountered in all classes of biomolecules
• saturated cyclic hydrocarbons have the formula CnH2n
• substituted cycloalkanes - named by identifying and numbering the location of the substituents on the carbon ring, followed by the name of the parent alkane
• name

  A) methylcyclohexane

  
• name

  A) 1,1-dimethylcyclohexane

  B) 1,3-dimethylcyclohexane

  C) 1,2-dimethylcyclohexane

  D) 1,4-dimethylcyclohexane