This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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4.1.1 Cracking is the process of breaking down long-chain hydrocarbons into shorter, more useful hydrocarbons (alkanes and alkenes) using heat and/or a catalyst.
4.1.2 Step 1: Determine the molecular formula of compound P. Heptane () is cracked into a FIVE CARBON alkane P and compound Q. The general formula for an alkane is . For a five-carbon alkane, . So, compound P is .
Step 2: Determine the molecular formula of compound Q. The total number of carbon atoms must be conserved: . The total number of hydrogen atoms must be conserved: . Therefore, the molecular formula for compound Q is .
The molecular formula for compound Q is .
4.1.3 The most important use of alkanes is as fuels.
4.1.4 Step 1: Write the unbalanced combustion reaction for compound P (). Complete combustion of a hydrocarbon produces carbon dioxide () and water ().
Step 2: Balance the carbon atoms. There are 5 carbon atoms on the left, so there must be 5 molecules on the right.
Step 3: Balance the hydrogen atoms. There are 12 hydrogen atoms on the left, so there must be 6 molecules on the right ().
Step 4: Balance the oxygen atoms. On the right side, there are oxygen atoms. To balance this, there must be 8 molecules on the left ().
The balanced equation for the complete combustion of compound P is:
4.2.1 The flow diagram shows a straight chain secondary haloalkane reacting to form a 5-carbon alcohol (Alcohol P), which then undergoes elimination to form (a 5-carbon alkene). This means the haloalkane must also have 5 carbon atoms. A straight chain secondary haloalkane with 5 carbons would have the halogen on the second or third carbon. Given the handwritten notes on the left, the halogen is on the second carbon. Since NaBr is a product of Reaction 1, the halogen is bromine. The IUPAC name is 2-bromopentane.
4.2.2 Reaction 1 is the conversion of a haloalkane to an alcohol. This is a hydrolysis reaction (or nucleophilic substitution).
4.2.3 Besides heat, another reaction condition for the hydrolysis of a haloalkane is an aqueous strong base (e.g., NaOH(aq) or KOH(aq)).
4.2.4 If the secondary haloalkane is 2-bromopentane, then Alcohol P, formed by replacing the bromine with a hydroxyl group, is pentan-2-ol. The structural formula of alcohol P is:
4.2.5 Reaction 2 is the conversion of an alcohol to an alkene (). This is an elimination reaction where water is removed from the alcohol. The name of this type of elimination reaction is dehydration.
4.2.6 Alcohol P is pentan-2-ol (). During dehydration, the -OH group and a hydrogen atom from an adjacent carbon are removed to form a double bond. According to Zaitsev's rule, the major product is the more substituted alkene. Removing H from C1 gives pent-1-ene (). Removing H from C3 gives pent-2-ene (). Pent-2-ene is the more substituted alkene and thus the major product. The structural formula for the product that was produced (pent-2-ene) is:
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4.1.1 Cracking is the process of breaking down long-chain hydrocarbons into shorter, more useful hydrocarbons (alkanes and alkenes) using heat and/or a catalyst.
This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.