ORGANIC MOLECULE GEOMETRY

Molecular Geometry

Molecular Geometry Types ||| Types II
 Elmhurst College
Alkanes Alkynes  Optical or Chiral  Chemistry Department
Alkenes ||| Cis / Trans Alkenes All Functional Groups Rings  Virtual ChemBook

Functional Groups and Molecular Geometry

Molecular geometry is associated with the specific orientation of bonding atoms. For organic molecules, we will observe the same types of geometry - linear, trigonal planar, tetrahedral, trigonal pyramid, and bent. When a molecule consists of many atoms, each carbon, oxygen, or nitrogen atom may be the center of the one of the geometries previously listed. The molecule as a whole will be the sum of all of the individual geometries to give an overall shape to the molecule. TAKE A QUIZ on the molecular geometry of the functional groups.

R = any number carbons in a hydrocarbon chain
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Functional
Group
Name

 General
Structure

 Structure

and Molecular Geometry

 Name
Graphic
Chime*

 Alkane

 CH3CH2CH3

All carbons have single bonds therefore the molecular geometry is TETRAHEDRAL. See alkanes.

Chime

 Alkene

 CH2=CHCH3

The main centers of interest are the carbons of the double bond. Each carbon is the center of a TRIGONAL PLANAR geometry. This portion of the molecule is flat, with bond angles of 120 degrees. See alkenes.

Chime

 Alkyne

 CH=CCH3

 

The main centers of interest are the carbons of the triple bond. Each carbon is the center of a LINEAR geometry. This portion of the molecule is in a straight line, with bond angles of 180 degrees. See alkynes.

Chime

Alcohol

R-OH

CH3CH2CH2OH

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the ether functional group is the oxygen. As in the water molecule there are two lone pairs of electrons on the oxygen in addition to the single bonds (invisible in the graphic), which give an electron pair geometry of tetrahedral.

This forces the molecular geometry on the alcohol oxygen to be BENT. This portion of the molecule is flat, with bond angles of 109 degrees.

Chime

 Ether

  R-O-R

 CH3CH2O-CH2CH3

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the ether functional group is the oxygen. As in the water molecule there are two lone pairs of electrons on the oxygen in addition to the single bonds (invisible in the graphic), which give an electron pair geometry of tetrahedral.

This forces the molecular geometry on the ether oxygen to be BENT. This portion of the molecule is flat, with bond angles of 109 degrees.

Chime

Aldehyde

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the aldehyde functional group is the carbon double bond oxygen.

With three atoms attached to this carbon, the molecular geometry is TRIGONAL PLANAR. This portion of the molecule is flat, with bond angles of 120 degrees. See formaldehyde.

Chime

Ketone

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the ketone functional group is the carbon double bond oxygen.

With three atoms attached to this carbon, the molecular geometry is TRIGONAL PLANAR. This portion of the molecule is flat, with bond angles of 120 degrees. See formaldehyde

Chime

 Acid

There are several centers of interest. The carbon with all single bonds is the center of a tetrahedral geometry.

The center of the acid functional group is the carbon double bond oxygen.

With three atoms attached to this carbon, the molecular geometry is TRIGONAL PLANAR. This portion of the molecule is flat, with bond angles of 120 degrees.

An additional molecular geometry is centered on the oxygen of the - OH group. This is BENT.

Chime

 Ester
 

There are several centers of interest. The two carbons with all single bonds is the center of a tetrahedral geometry.

The center of the ester functional group is the carbon double bond oxygen.

With three atoms attached to this carbon, the molecular geometry is TRIGONAL PLANAR. This portion of the molecule is flat, with bond angles of 120 degrees.

An additional molecular geometry is centered on the oxygen with all single bonds. This is BENT.

Chime

 Amine

 R-NH2
or
R-NH-R

 CH3CH2CH2NH2

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the amine functional group is the nitrogen. As in the ammonia molecule there is one lone pair of electrons on the nitrogen in addition to the single bonds (invisible in the graphic), which give an electron pair geometry of tetrahedral.

This forces the molecular geometry on the amine nitrogen to be a TRIGONAL PYRAMID. This portion of the molecule is NOT flat, with bond angles of 109 degrees.

Chime

 Amide

 

There are several centers of interest. Each carbon with all single bonds is the center of a tetrahedral geometry.

The center of the amide functional group is the carbon double bond oxygen and the nitrogen.

With three atoms attached to this carbon, the molecular geometry is TRIGONAL PLANAR. This portion of the molecule is flat, with bond angles of 120 degrees.

An additional molecular geometry is centered on the nitrogen through an exceptional circumstance of the bonding. This is BENT and also flat as an extension of the trigonal planar geometry.

Chime