a. There are 18 isomeric alkanes of molecular formula C 8 H 18 . Draw and name any eight of them.

Welcome back everyone to the isomers of an L Kane with the molecular formula of C five H 12 and give the IEC names of the isomers. We're looking at L canes. And whenever we want to draw isomers, the easiest way is to, first of all, draw the longest possible continuous carbon chain. If we have five carbon atoms, we're going to draw 1234 and five carbon atoms in the longest continuous chain. So that would be normal and sane, right? Because that's C five H 12, we don't need to count the atoms since we don't have any double or triple bonds, all of our bonds are single bonds and the structure is saturated, right? So if we added five carbon atoms, there will be 12 hydros. So we have one of our structures. Now, what is the next structure that we can draw? We essentially want to shorten the chain and instead of having five carbon atoms, we are going to draw four and the remaining carbon atom will act as a substituent and we can add it to carbon too ripe. So that's our next structure which is to methyl butane because the parent has four carbons. So that's butane, if we enumerate it, carbon number two has a methyl group. So we're going to say two methyl be in, that's the name of the structure. Now, what is the next structure that we can draw? Can it, can we shorten it even more? We cannot move that methyl subscription to carbon number three because that carbon three becomes carbon two, right. We essentially want to minimize the locus. So we change the numbering from right to left. And instead, so the only thing that we can do is try to shorten the chain to three carbon atoms and add two remaining carbon atoms as substituents specifically, they become two metal groups. And this looks like a new structure, right? Because it contains a quaternary carbon. Now, the parent is propane because we have three carbon atoms in the longest continuous chain. So that's propane and carbon two contains two metal groups. So we have to write two comma two. We're going to use a prefixed dye because there are two metal groups. So the structure would be two to dimethyl propane. Can we draw any additional structures? Well, we cannot because we have already used up the shortest possible remember chain for our isomers. And that's it. We have three structures. We can conclude the video. Thank you for watching.

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1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

4. Alkanes and Cycloalkanes

IUPAC Naming

Organic Chemistry

4. Alkanes and Cycloalkanes

IUPAC Naming

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3:27 minutes

Problem 33a

Textbook Question

a. There are 18 isomeric alkanes of molecular formula C₈H₁₈. Draw and name any eight of them.

Verified step by step guidance

Step 1: Understand the concept of isomerism. Isomers are compounds with the same molecular formula but different structural arrangements. In alkanes, isomerism arises due to different branching patterns.

Step 2: Start with the simplest structure, the straight-chain alkane. For C8H18, this is n-octane. Draw a linear chain of eight carbon atoms, each bonded to sufficient hydrogen atoms to satisfy the tetravalency of carbon.

Step 3: Create branched isomers by rearranging the carbon atoms. Begin by shortening the main chain and adding branches. For example, draw 2-methylheptane by having a seven-carbon chain with a methyl group (CH3) attached to the second carbon.

Step 4: Continue creating isomers by varying the position and number of branches. For instance, draw 3-methylheptane, 2,2-dimethylhexane, and 2,3-dimethylhexane. Ensure each structure has eight carbon atoms and eighteen hydrogen atoms.

Step 5: Name each isomer according to IUPAC nomenclature rules. Identify the longest carbon chain, number the chain to give the lowest numbers to the substituents, and list substituents alphabetically. Verify that each name corresponds to a unique structure.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isomerism

Isomerism refers to the phenomenon where compounds have the same molecular formula but different structural arrangements. In organic chemistry, structural isomers differ in the connectivity of atoms, leading to variations in physical and chemical properties. Understanding isomerism is crucial for identifying and drawing different isomeric forms of a given compound.

Alkanes

Alkanes are saturated hydrocarbons consisting solely of carbon and hydrogen atoms, connected by single bonds. They follow the general formula CnH2n+2, where n is the number of carbon atoms. Alkanes are characterized by their lack of reactivity due to the stability of C-C and C-H bonds, making them a fundamental class of compounds in organic chemistry.

IUPAC Nomenclature

IUPAC nomenclature is a standardized system for naming chemical compounds, ensuring clarity and consistency in communication. For alkanes, the name is derived from the longest carbon chain, with prefixes indicating the presence and position of branches or substituents. Mastery of IUPAC rules is essential for accurately naming and identifying different isomers.

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