Writing Structures

1
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

2
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

Butane C4H10
3
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

Butane C2H5
4
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

H H H H Butane H C
C C C H H H H
H
5
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

Butane CH3CH2CH2CH3

6
Writing Structures

• Molecular formula - atoms in a molecule
• Empirical formula ratio of elements
• Structural formula atom to atom bonding
• Condensed formula
• 3-D drawing

H H H H
H C C H Butane H C
C H H H
Correct bond angles would be shown
7
Condensed formulas

• Groups are written
• An understanding of bonding is assumed
• H only bonds to one atom (C, O or N)
• Bound to atom it follows (Usually)

H H H H Butane H C
C C C H H H H
H
CH3 CH2 CH2 CH3
CH3CH2CH2CH3
8
Condensed formulas

• Parentheses can be used
• CH3(CH2)2CH3 CH3CH2CH2CH3 butane
• (CH3)2CHCH3 CH3
• 
  CH-CH3
• 
  CH3 2-methyl propane

9
Organic Shorthand

• Condensed formulas take a long time to write for
  all but the smallest molecules
• Shorthand gives the carbon backbone and assumes
  an understanding of the remaining bonding in the
  molecule
• Gives better idea of bond angles than condensed
  formulas

10
Shorthand

• The end of a line segment is a carbon
• A corner or the center of two line segments
  crossing is a carbon

CH3CH2CH3 CH3CHCH2CH3 CH3
11
Shorthand

• Multiple bonds and heteroatoms (not C or H) are
  possible

CH3CH CHCH3 OH CH3CH-CH-CH3
OH CH3
12
Other symbols

• R means any carbon chain in a shorthand or a
  condensed structure
• X means any halogen

Any carbon chain

H RCHCH2 C C
H H CH3X
CH3Cl, CH3Br, CH3I usually not F
as its chemistry is different from the
others