Multiple Choice
What is the correct IUPAC name for the compound with the structure ?
4. Alkanes and Cycloalkanes
IUPAC Naming
5:15 minutesProblem 9
Textbook Question
Without looking at the structures, give molecular formulas for the compounds: (a) 4-(1,1-dimethylethyl)octane and (b) 5-(1,2,2-trimethylpropyl)nonane. Use the names of the groups to determine the number of carbon atoms; then use the (2n + 2) rule.
Verified step by step guidance1
Step 1: Begin by identifying the main chain in each compound. For compound (a), the main chain is octane, which has 8 carbon atoms. For compound (b), the main chain is nonane, which has 9 carbon atoms.
Step 2: Identify the substituents attached to the main chain. In compound (a), the substituent is 4-(1,1-dimethylethyl), which consists of a tert-butyl group. This group has 4 carbon atoms. In compound (b), the substituent is 5-(1,2,2-trimethylpropyl), which consists of a group with 6 carbon atoms.
Step 3: Add the number of carbon atoms from the main chain and the substituents. For compound (a), add 8 (from octane) and 4 (from the tert-butyl group) to get the total number of carbon atoms. For compound (b), add 9 (from nonane) and 6 (from the trimethylpropyl group) to get the total number of carbon atoms.
Step 4: Use the general formula for alkanes, CnH2n+2, to determine the number of hydrogen atoms. For compound (a), substitute the total number of carbon atoms into the formula to find the number of hydrogen atoms. Repeat the process for compound (b).
Step 5: Combine the number of carbon and hydrogen atoms to write the molecular formula for each compound. Ensure that the formula reflects the total number of each type of atom present in the compound.
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5mKey Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
IUPAC Nomenclature
IUPAC nomenclature is a systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC). It provides a standardized way to describe the structure of a compound using specific rules, which include identifying the longest carbon chain, numbering the chain, and naming substituents.
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Alkyl Groups
Alkyl groups are groups of carbon and hydrogen atoms arranged in a chain, derived from alkanes by removing one hydrogen atom. They are named based on the number of carbon atoms they contain, such as methyl (CH3), ethyl (C2H5), and propyl (C3H7). Understanding alkyl groups is crucial for determining the structure and molecular formula of complex organic compounds.
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Molecular Formula Calculation
The molecular formula of an alkane can be determined using the general formula CnH2n+2, where n is the number of carbon atoms. This formula accounts for the saturated nature of alkanes, which have single bonds between carbon atoms. By identifying the number of carbon atoms in the main chain and substituents, one can calculate the total number of hydrogen atoms to derive the molecular formula.
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