Structures of Alkanes
Naming, Drawing, and Structural Formulae for Alkanes
Alkanes• Also known as saturated hydrocarbons• Made on C and H• In hydrocarbons C is bonded to H and maybe C while H is only bonded to C• C has 4 valence electrons and needs to share another 4 electrons to make
an octet
Consider Methane with the formula CH4 this is the simplest alkane
CH4
Lewis dot structure
Complete Structural formula
Condensed structural formula
3-dimensional structure
Names of AlkanesThe names all end in “ane”, the prefix depends on how many carbons are in the alkane
Constitutional Isomers
• When the molecular formula can be drawn with different structures
• Consider butane C4H10
complete structural formulae
geometric formula
Cycloalkanes• In a cycloalkane a group of C atoms form a ring• Consider Cyclobutane C4H8
Complete StructuralFormula
Geometric Formula
CondensedFormula
3-dimensionalstructure
Haloalkanes
• In a haloalkane a halogen like Cl or Br replaces one of the H atoms in the alkane
CH3Cl Chloromethane
BrCH2CH2Br 1,2 dibromoethane
A. Structure of Alkanes• Make a model and write out (i) the 3-d structure, (ii) complete structure
formula and (iii) condensed structural formula for• CH4 (methane), C2H6 (ethane), and C3H8 (propane)
B. Constitution isomers• Make a model and write out (i) the 3-d structure, (ii) complete structure
formula and (iii) condensed structural formula for• C4H10 (butane), and 2-methyl-propane (isobutane)
• The 3 isomers of pentane C5H12
C. Cycloalkanes• Make a model and write out (i) the 3-d structure, (ii) complete structure
formula and (iii) condensed structural formula for• A ring structure involving 3 carbon atoms• A ring structure involving 5 carbon atoms
D. Haloalkanes• Make a model and write out (i) the 3-d structure, (ii) complete structure
formula and (iii) condensed structural formula for• Chloromethane, 1,2 dibromoethane, 2-iodopropane, 4 isomers of
dichloropropane
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