Molecular Modeling Lab
Introduction to Microscale Laboratory – Prelab Instructions Read pages 1-12 in your lab manual and follow the prelab report format for the procedures in lab exercises 1 & 2 (pp. 9-11) . This written work must be done in your lab notebook and must be completed before coming to the lab. Molecular Modeling Print this handout and bring it to the lab with you. You do not need to do any prelab work for the molecular modeling part of the lab. Answer these questions in your lab notebook in the post lab question section of your lab report. You may work together to build the models.
There are many organic substances that have identical molecular formulas but are completely different compounds. Consider the molecular formula C2H6O. There are two compounds that correspond to this formula: ethyl alcohol and dimethyl ether. While the molecular formula gives no clue as to which compound one may be referring, examination of the structural formula immediately reveals a different arrangement of atoms for these substances. Compounds that have the same molecular formula but different structural formulas are termed isomers.
In this lab exercise, you will determine the different isomers for various alkane (CnH2n+2) molecules. For each question, you will be asked to provide the structural formula, the condensed formula, and the IUPAC name. Structural Formula: H H ¦ ¦ H – C — C – O – H ¦ ¦ H H Condensed Formula: CH3CH2OH IUPAC name: Ethanol H H ¦ ¦ H – C — O — C – H ¦ ¦ H H CH3OCH3 methoxymethane PROCEDURE: Construct models of the alkane molecules as directed below and identify all the possible isomers. Use two black U pieces to form the sp3 carbon atom, a white ball for hydrogen, and a green ball for chlorine.
Hint: the number in parenthesis for each question represents the number of isomers for each compound. Answer all questions in your lab notebook A. Methane (CH4) Construct a model of methane. Place the model on the desk top and note the symmetry of the molecule. Note that the molecule looks the same regardless of which three hydrogens are resting on the desk. All four hydrogens are equivalent. Replace one of the hydrogen atoms with a chlorine atom to construct CH3Cl. Replace a second hydrogen with another chlorine atom to make CH2Cl2. Repeat to make CHCl3 and CCl4. . Draw the structural formula and write the IUPAC name for each of the chloromethanes. (4) B. Ethane (C2H6) Make a model of ethane by joining two methyl groups (CH3). Replace one hydrogen with chlorine. Does it matter which carbon the chlorine is associated with? 1. Write the structural and condensed formulas and IUPAC name for C2H5Cl 2. Write the structural and condensed formulas for all isomers of C2H4Cl2 and assign IUPAC names to each. (2) C. Propane (C3H8) Construct a model of propane and note how many different hydrogen atoms are present.
If one of the hydrogens is replaced with chlorine, how many isomers are there corresponding to the formula C3H7Cl? 1. Write the structural and condensed formulas and the IUPAC names for all the isomers of C3H7Cl (2) 2. Write the structural and condensed formulas and the IUPAC names for all the isomers of C3H6Cl2 (4) 3. Write the structural and condensed formulas and the IUPAC names for all the isomers of C3H5Cl3 (5) D. Butane (C4H10) Construct a model of butane and note how many different hydrogen atoms are present. 1.
Write the structural and condensed formulas and the IUPAC names for all butanes. (2) 2. Write the structural and condensed formulas and the IUPAC names for all the isomers of C4H9Cl (4) 3. Write the structural and condensed formulas and the IUPAC names for all the isomers of C4H8Cl2 (9) E. Pentane C5H12 Construct a model of pentane and note how many different hydrogen atoms are present. 1. Write the structural and condensed formulas and the IUPAC names for all the isomers of pentane. (3) 2. Write the structural and condensed formulas and the IUPAC names for all the isomers of C5H11Cl (8)
