An unknown hydrocarbon A with the formula C6 H12 reacts with 1 molar equivalent of H2 over a pal

step 1 Here question number 44. An unknown hydrocarbon A with the formula C6H12 reacts with one molar e

An unknown hydrocarbon A with the formula C6 H12 reacts with...

An unknown hydrocarbon A with the formula $\mathrm{C}_{6} \mathrm{H}_{12}$ reacts with 1 molar equivalent of $\mathrm{H}_{2}$ over a palladium catalyst. Hydrocarbon $\mathrm{A}$ also reacts with OsO_ to give diol B. When oxidized with KMnO_in acidic solution, A gives two fragments. One fragment is propanoic acid, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CO}_{2} \mathrm{H},$ and the other fragment is ketone $\mathbf{C .}$ What are the structures of $\mathbf{A}, \mathbf{B},$ and $\mathbf{C} ?$ Write all reactions, and show your reasoning.

Key Concepts

Alkene Substitution and Reaction Outcome

The substitution pattern at the double bond can influence the products formed upon oxidation. A sp^2 carbon lacking hydrogen (due to heavy alkyl substitution) tends to yield a ketone upon oxidative cleavage, whereas a carbon with at least one hydrogen can be further oxidized into a carboxylic acid. This concept is critical for deducing the structure of the original alkene from its oxidation fragments.

Oxidative Cleavage of Alkenes/Diols with KMnO?

Oxidative cleavage with potassium permanganate under acidic conditions breaks the carbon–carbon double bond (or the diol linkage) to form carbonyl-containing fragments. The nature of the oxidation products, such as carboxylic acids from carbons that have hydrogens and ketones from fully substituted carbons, provides key insight into the substitution pattern of the original alkene.

Structure Determination via Reaction Products

Analyzing the reaction products—such as the simultaneous formation of a carboxylic acid fragment (propanoic acid) and a ketone fragment (e.g., acetone)—provides clues about how the carbon chain is divided in the original molecule. This approach is a common method in organic synthesis for elucidating the structure of unknown compounds by correlating the outcomes of specific chemical reactions with underlying structural features.

Hydrogenation of Alkenes

Hydrogenation is the catalytic addition of hydrogen to unsaturated bonds, such as carbon–carbon double bonds. In this reaction, the alkene reacts with H? over a palladium catalyst to form a saturated alkane. This concept is important because it confirms the presence of a single double bond in the molecule, and the stoichiometry (one equivalent of hydrogen) indicates the degree of unsaturation in the original compound.

Dihydroxylation Using OsO?

Dihydroxylation is the syn addition of two hydroxyl groups across a double bond using osmium tetroxide, yielding a vicinal diol. This reaction is stereospecific and provides information about the configuration of the original alkene. In a structural determination problem, obtaining a diol upon oxidation helps confirm the position of the double bond in the hydrocarbon.

Transcript

00:03 Here question number 44.

00:06 An unknown hydrocarbon a with the formula c6h12 reacts with one molar equivalent of hydrogen over a palladium catalyst.

00:19 Now in such kind of question actually with this reading, you must make the flow chart so the things will be more clear.

00:31 And you are starting with a compound so about the a compound it is given that its formula is c6 and h12 this is indicating one double bond must be present in it and with it is reacting with one molar one mole hydrogen hydrogen in presence of palladium catalyst.

01:22 So this is further indicating that one double bond must be present.

01:26 This is catalytic hydrogenation addition of hydrogen at the double bond.

01:32 So this much information we are getting by this first sentence.

01:38 Hydrocarbon a also reacts with osmium tetraoxide to give a diol.

01:45 So one more information that a compound can react with osmium tetraoxide this reaction is also important double bond reaction to give diol b one b compound is formed that is actually a diol so this much is up to here when oxidized with k -manof -4 in acidic solution one more information about a.

02:32 This can react with acidified k -manophor, k -manof -4 in presence of acid.

02:48 Acidic solution, a gives two fragments.

02:53 Two fragments are formed.

02:55 One fragment is propanoic acid.

02:58 So cleavage is taking place at the double bond and by that you should get two fragments and one fragment is clear.

03:10 It is ch3, ch2, cooh.

03:21 And the other fragment is keto...

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