week 1 - 4 - anno

week 1 - 4 - anno - Chemistry S-20ab Chemistry E-2a Lecture...

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An Introduction to Alkenes Draw the skeletal structures of all hydrocarbons with the formula C 4 H 8 . What can we note about these structures? Some of the above structures contain a C=C double bond. What orbitals are involved in a C=C double bond? What do we call different molecules that have the same molecular formula? Reading : Section 4.1 Chemistry S-20ab Week 1 49
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Naming Alkenes Each of the following names describes an alkene. However, these names are not the correct names for these molecules. Draw the skeletal structure of the molecule and provide a correct systematic name. 4-ethyl-4-pentene 2-vinylpropane allylethane Reading : Section 4.2 Chemistry S-20ab Week 1 50
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Chemistry S-20ab Week 1 51 The Problem with Cis and Trans How would you name the following alkenes? A : B : We need better rules: The E / Z rules for naming alkanes require that we determine the priority of the four groups attached to the alkene, as follows: Step 1 . Greater atomic number = higher priority. If atomic number is the same, heavier isotope = higher priority. If there is a tie , go on to Step 2. Step 2. If the atoms are the same, consider the atoms that are attached. (For carbon, there will be 3 other atoms). List those atoms in descending order of priority, and make a pairwise comparison between the two sets. One “wins” at the first point of difference. If there is a tie , go on to Step 3. Step 3. If the two sets of atoms are the same, follow the path of highest priority and move one atom away along each path. Then go back to Step 2, but with the new atoms. Continue in this fashion until one of the branches ultimately “wins” over the other. Step 4.
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week 1 - 4 - anno - Chemistry S-20ab Chemistry E-2a Lecture...

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