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Alkanes, Alkenes, and Alkynes: Naming and Classification

ALKANES

Main Idea

  • Definition of Alkane: An alkane is an organic molecule that contains only carbon (C) and hydrogen (H) atoms, and only single bonds between them.

  • The carbon and hydrogen atoms of an alkane can be arranged in various configurations.

  • Constitutional Isomers: Alkanes with the same number of carbon and hydrogen atoms but different arrangements.

Skills to Master

  1. Draw a constitutional isomer of a molecule.

  2. Determine if a pair of molecules are constitutional isomers of each other.

  3. Identify the correct name of a straight-chain alkane.

  4. Identify the correct name of a cyclic alkane.

  5. Identify the correct name of a halogenated alkane (straight-chain or cyclic).

Terminology

  • Alkane (al-CANE)

  • Alkyl halide (al-KILL HAY-lide)

  • Branched alkane

  • Constitutional isomer

  • Cycloalkane (sigh-CLOW al-CANE)

  • Parent chain

  • Substituent (sub-STITCH-you-ent)

NAMING ALKANES

Steps for Naming Alkanes

  1. Classify each pair of molecules as constitutional isomers, the same molecule, or neither.

  2. Follow these steps to name the substituted alkane:

    • a. Find the longest carbon chain (the parent chain).

    • b. Number the carbon chain starting from the end closest to the substituent.

    • c. Locate and name the substituent.

    • d. Put the substituent in front of the parent chain, all as one word. Name: _

  3. If you have more than one substituent, arrange in alphabetical order, not numerical.

  4. For identical substituents, number them both individually and use “di-“ to indicate that there are two.

  5. In a cycloalkane, choose where carbon #1 is based on substituents, without mentioning carbon #1 if only one sub.

  6. If multiple substituents in a cycloalkane, put them in alphabetical order, starting with the first in naming.

  7. Name the four pairs of molecules provided at the beginning of the worksheet.

UNSATURATED HYDROCARBONS (ALKENES AND ALKYNES)

Main Idea

  • An unsaturated hydrocarbon contains at least one double bond (alkene) or triple bond (alkyne) between carbon atoms.

  • Alkenes: Hydrocarbons with a double bond.

  • Alkynes: Hydrocarbons with a triple bond.

Skills to Master

  1. Identify and name straight-chain and cyclic alkenes.

  2. Identify and name straight-chain and cyclic alkynes.

  3. Identify cis and trans isomers of alkenes.

  4. Predict the product of hydrogenation of an alkene.

  5. Predict the product of halogenation of an alkene.

  6. Apply Markovnikov’s rule in hydration and hydrohalogenation reactions of alkenes.

  7. Classify a molecule as aromatic or not.

Terminology

  • Alkene (al-KEEN)

  • Alkyne (al-KINE)

  • Aromatic

  • Benzene (ben-ZEEN)

  • Cis

  • Markovnikov’s rule (mar-KOV-ni-kov)

ALKENES AND ALKYNES

Steps for Naming Alkenes and Alkynes

  1. Identify the longest carbon chain containing the double or triple bond.

  2. Number the chain starting at the end closest to the double or triple bond, even if substitutes are present.

  3. Locate all substituents and name them in alphabetical order.

  4. Indicate the position of the double or triple bond in the name.

  5. Modify the parent chain name:

    • Change the ending from “-ane” to “-ene” for double bonds, or “-yne” for triple bonds.

Cis-Trans Isomers

  • Classify each alkene as cis, trans, or neither. Practice naming as many alkenes as possible.

REACTION OF ALKENES

Products of Reactions

  • Draw the product for each kind of reaction listed in provided content.

INTRODUCTION TO ALKANES

Types of Alkanes

  • Straight-Chain Alkanes: Continuous linear arrangement of carbon atoms.

  • Cyclic Alkanes: Carbon atoms arranged in a loop or ring shape, e.g., cyclobutane.

Naming Alkanes

  • Names are derived from the number of carbon atoms present:

    • 1 C: Methane

    • 2 C: Ethane

    • 3 C: Propane

    • 4 C: Butane (straight-chain) / Cyclobutane (cyclic)

    • 5 C: Pentane / Cyclopentane

    • 6 C: Hexane / Cyclohexane

    • 7 C: Heptane / Cycloheptane

    • 8 C: Octane

    • 9 C: Nonane

    • 10 C: Decane

Naming Conventions

  • Straight chain alkanes: use the common name according to the number of carbon atoms.

  • Cyclic structures: add prefix "cyclo" before the alkane name.

NAMING ALKANES WITH BRANCHES

Definition of a Branch

  • A branch refers to additional carbon atoms/groups that are attached to the main carbon chain.

Steps for Naming Molecules with Branches

  1. Identify the longest continuous chain.

  2. Number carbon atoms closer to branches.

  3. Name the molecule combining location and names of substituents (e.g., 2-methyl).

  4. For multiple identical substituents, use “di-” and list their locations.

  5. For different substituents, name them alphabetically regardless of position numbers.

Example Naming with Different Substituents

  • For additional branches identify main chain, then include substituent names in alphabetical order: e.g., 4-ethyl-3-methylheptane.

Additional Naming Considerations

  • Precedence in naming: maintain ordering, use dashes for numbers and letters.

  • All substituents have location numbers even if identical.

NAMING ALKANES WITH HALOGENS

Basic Naming Principles

  • Comprehend how to name alkanes incorporating halogens, paralleling previous nomenclature rules.

Halogen Names as Substituents

  • Fluorine: Fluoro

  • Chlorine: Chloro

  • Bromine: Bromo

  • Iodine: Iodo

Examples

  1. Single Halogen on Alkane: Identify longest chain, apply halogen naming and combine with parent alkane name.

  2. Multiple Substituents: Identify chain length, number substituents, list alphabetically, and combine with parent alkane name.

Final Naming Summary

  • Clarity in attaching halogens is essential, including listing locations, thus ensuring systematic approach in chemical nomenclature.

NAMING CYCLIC ALKANES WITH BRANCHES OR HALOGENS

General Rules

  • Identify the longest ring and number based on substituent location, noting the alphabetical order.

  • Include numbers in naming for each substituent in the molecule.

Examples of Compounds

  1. Cycloalkanes with Single Substituents: Named without their position if only one.

  2. Cycloalkanes with Multiple Substituents: Name according to the alphabetical positioning based on substituent types.

Summary of Naming Cycloalkanes

  • Maintaining consistency and following traditional nomenclature leads to accurate chemical names.

CLASSIFICATION OF MOLECULES

Purpose of Classification

  • Establish the relationship between pairs of molecules in terms of structural isomerism and equality of formulae.

Evaluation Steps

  1. Count the number of C and H atoms to see if they share a molecular formula.

  2. Check the connectivity of these atoms to determine if they are identical or isomers.

Examples

  1. Identical Molecules: Analysis of similar structures.

  2. Constitutional Isomers: Different connectivity but the same molecular formula.

  3. Neither: Different molecular formulas.

Common Problems in Classification

  • Understand various arrangements may lead to structural diversity, thus impacting chemical properties.

NAMING ALKANES - GENERAL STEPS

Steps to Naming Alkanes

  1. Identify and count carbons in the longest chain.

  2. Number from the nearest substituent’s end.

  3. Locate and name substituents, combining in the full name.

Example of Two Substituents

  • Recognizing complex branches, count paths, and prioritize based on alphabetical ordering when constructing names.

Advanced Considerations in Naming

  • Maintain proper notation when naming to follow established IUPAC norms, ensuring clarity and structure integrity.

Solutions for Practical Applications

  • During naming exercises, aligning theoretical knowledge with applicable practical problems yield comprehensive understanding of organic nomenclature foundations.

OVERVIEW OF NAMING AND DRAWING BRANCHED ALKANES

Types of Problems to Solve

  1. Given three molecules, derive their names (Version 1).

  2. Given the name of a molecule, draw its structure (Version 2).

Procedure for Naming Molecules

  1. Identify the longest continuous carbon chain making it straightforward to designate.

  2. Number the chain based on proximity to substituents.

  3. Constructing names will encapsulate alphabetical arrangements for effective communication in chemical nomenclature.

Summary

  • Concentrate on practice problems showcasing both naming and drawing to solidify comprehension of structural chemistry.

SUMMARY OF CONCEPTS

  • Recommendations encourage an intricate understanding of nomenclature leading to proficient identification and representation of organic structures efficiently.

  • Suggested focus on applying and drawing analogues with iterative practice through constant reiteration of primary structures and functional chemistry principles.