Stabilities of alkanes can be compared by converting these compounds to a common product and comparing the amount of the heat given off. One possiblitiy would be to measure the heat of combustion from converting alkenes to `xo_(2)` and `H_(2)O` . The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable.
Th stability of alkenes is often compared by meansuring the ehat of hydrogenation `9` heat given off, `Delta H_(h)^(@)` during catalytic hydrogenation. The heat of hydrogenation is in smal number, which provides more accurate energy difference.
For a compound containing more than one double bond, `Delta_(h)^(@)` is the sum of heat of hydrogenation of individual double bonds. For non `-` conjugated diens, this additive relatioship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non `-` conjugated dienes.
The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strin are less stable.
The wrong option among the following statements is `:`

Options

A. The decreasing order of the value of the heat of combustion is `:`

B. Cycloalkanes are planar
C. Cyclopropane has a higher heat of combustion per methylene group `(CH_(2))` than of cyclobutane.
D. With the exception of cyclpropane, cycloalkanes are non`-` planar.

Explanation

To solve the question regarding the stability of alkenes and identify the wrong statement among the provided options, we will follow these steps:

### Step 1: Understand the Concept of Stability in Alkenes
The stability of alkenes can be assessed by measuring the heat of combustion and the heat of hydrogenation. Lower heat values indicate more stable alkenes.

### Step 2: Analyze the Heat of Combustion
- The heat of combustion is a large value, and the alkene with the lowest heat of combustion among isomeric alkenes is the most stable.
- This means that as the stability of alkenes increases, the heat of combustion decreases.

### Step 3: Analyze the Heat of Hydrogenation
- The heat of hydrogenation (ΔH_h) is a more accurate measure for comparing alkene stability because it is a smaller number.
- For compounds with multiple double bonds, the heat of hydrogenation is the sum of the heats of individual double bonds.
- Non-conjugated dienes follow this additive relationship, while conjugated dienes have slightly lower measured values than expected.

### Step 4: Evaluate the Statements
Now, we will evaluate the statements provided in the question to identify the incorrect one:

1. **Statement 1**: The decreasing order of the value of the heat of combustion is correct based on the stability of the structures.
2. **Statement 2**: Cycloalkanes are planar. This statement is incorrect because cycloalkanes, especially cyclopropane and cyclobutane, have non-planar conformations due to angle strain.
3. **Statement 3**: Cyclopropane has a higher heat of combustion per methylene group than that of cyclobutane. This statement is correct due to cyclopropane's higher strain and lower stability.
4. **Statement 4**: With the exception of cyclopropane, cycloalkanes are non-planar. This statement is also correct.

### Step 5: Identify the Wrong Option
From the analysis, **Statement 2** is the wrong option because cycloalkanes are not planar.

### Final Answer
The wrong option among the statements is: **Cycloalkanes are planar.**

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