Textbook Question
How many of the following names are correct? Correct the incorrect names.
g. 2-ethyl-2-butene
h. (E)-2-methyl-1-hexene
i. 2-methylcyclopentene
4. Alkanes and Cycloalkanes
Naming Alkenes
3:36 minutesProblem 9a,b
Textbook Question
Draw the structure for each of the following:
a. 3,3-dimethylcyclopentene
b. 6-bromo-2,3-dimethyl-2-hexene
Verified step by step guidance1
Step 1: For part (a), start by identifying the parent structure. The parent structure is 'cyclopentene,' which is a five-membered ring containing one double bond. Draw a cyclopentene ring with one double bond in the structure.
Step 2: Add the substituents to the cyclopentene ring. The name '3,3-dimethyl' indicates that there are two methyl groups attached to the third carbon of the cyclopentene ring. Number the ring carbons such that the double bond gets the lowest possible number (1 and 2). Place the two methyl groups on carbon 3.
Step 3: For part (b), identify the parent structure. The parent structure is '2-hexene,' which is a six-carbon chain with a double bond between carbons 2 and 3. Draw a six-carbon chain and place a double bond between carbons 2 and 3.
Step 4: Add the substituents to the hexene chain. The name '6-bromo' indicates a bromine atom attached to carbon 6, and '2,3-dimethyl' indicates methyl groups attached to carbons 2 and 3. Number the chain such that the double bond gets the lowest possible number (2). Place the bromine atom on carbon 6 and the methyl groups on carbons 2 and 3.
Step 5: Verify the structures for both parts (a) and (b) to ensure that all substituents are correctly placed, the double bonds are in the correct positions, and the structures follow the IUPAC naming conventions.
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3mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cycloalkenes
Cycloalkenes are cyclic hydrocarbons that contain at least one carbon-carbon double bond. In the case of 3,3-dimethylcyclopentene, the structure consists of a five-membered carbon ring with two methyl groups attached to the third carbon. Understanding the geometry and bonding in cycloalkenes is crucial for accurately drawing their structures.
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Substituent Positioning
In organic chemistry, the positioning of substituents on a carbon chain or ring is essential for defining the compound's structure and properties. For 6-bromo-2,3-dimethyl-2-hexene, the numbers indicate the specific locations of the bromine and methyl groups on the hexene chain, which is a six-carbon alkene. Correctly identifying these positions is vital for drawing the accurate molecular structure.
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Double Bonds and Stereochemistry
Double bonds in alkenes introduce geometric isomerism due to restricted rotation around the bond. In 6-bromo-2,3-dimethyl-2-hexene, the presence of the double bond at the second carbon can lead to cis/trans isomerism, affecting the compound's physical and chemical properties. Recognizing the implications of double bonds and their stereochemistry is important for understanding the overall structure.
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