Organic Chemistry: Carbon Bonding and Synthesis

• Carbon can uniquely form covalent bonds with other carbon atoms, it is called catenation
• Carbon also forms covalent bonds with hydrogen, oxygen, nitrogen, sulfur, phosphorus, and halogens
• Organic chemistry focuses on the study of carbon-containing compounds and their properties
• Organic compounds crucial for life, including DNA and proteins
• They are found in clothing, fuels, polymers, dyes, and medicines

General Introduction

• Around 1780, chemists distinguished between organic (from plants and animals) and inorganic (from minerals) compounds
• Berzilius proposed a 'vital force' was responsible for organic compound formation
• In 1828, Wohler synthesized urea from ammonium cyanate, disproving the vital force theory

Pioneering Synthesis

• Kolbe synthesized acetic acid in1845
• Berthelot synthesized methane in 1856
• These showed organic compounds can be made from inorganic sources in labs

Tetravalence of Carbon

• The electronic theory of covalent bonding shaped modern organic chemistry
• Knowledge of molecular structure is fundamental to understanding organic compound properties

Shapes of Carbon Compounds

• Tetravalence and covalent bond formation are explained by electronic configuration and s/p orbital hybridization
• Methane (CH4), ethene (C2H4), and ethyne (C2H2) use sp3, sp2, and sp hybrid orbitals, respectively

Hybridization Influence

• Hybridization affects bond length and enthalpy
• Greater s character in hybrid orbitals leads to shorter, stronger bonds
• sp hybrid orbitals have more s character, so they are closer to the nucleus leading to shorter and stronger bonds than sp3 orbitals
• sp2 orbitals are intermediate in s character and bond properties between sp and sp3

Electronegativity

• Hybridization affects carbon's electronegativity; greater s character increases electronegativity
• An sp hybridized carbon is more electronegative than sp2 or sp3 hybridized carbons
• This electronegativity influences physical and chemical properties

Features of π Bonds

• π bond formation requires parallel orientation of p orbitals on adjacent atoms for sideways overlap
• In H2C=CH2, all atoms are in the same plane; p orbitals are mutually parallel and perpendicular to the molecule's plane

Rotation Restriction

• Rotation of CH2 fragments in double bonds restricts p orbital overlap
• π bond electron charge cloud is located above and below the plane of bonding atoms
• Allows electrons to be readily available for attacking reagents

Reactive Centers

• π bonds provide the most reactive centers in molecules

Structural Formulas

• Organic structures use Lewis dot, dash, condensed, and bond-line formulas
• Lewis structures are simplified by representing two-electron covalent bonds as dashes

Electron Focus

• Structural formulas focus on electrons in bond formation
• Single, double, and triple bonds are represented by single, double, and triple dashes, respectively
• Lone pairs on heteroatoms may or may not be shown

Complete Structural Formulas

• Ethane (C₂H₂), ethene (C₂H₄), ethyne (C₂H₂) and methanol (CH3OH) structures can have complete structural formuals

Abbreviated Formulas

• Structural formulas can be abbreviated by omitting dashes or showing identical groups with subscripts
• These resulting expressions are condensed structural formulas
• Ethane, ethene, ethyne, and methanol can be written as CH3CH3, H₂C=CH2, HC=CH, CH3OH, respectively

Further Simplification

• Organic chemists use line representations where carbon and hydrogen atoms are not shown and carbon-carbon bonds are zig-zag lines
• Terminals denote methyl groups (-CH3), and line junctions denote carbon atoms bonded to appropriate hydrogens

Example Representations

• 3-Methyloctane can be represented as:
  • CH₂CH₂CHCH₂CH₂CH₂CH₂CH₂
  • CH
  • CH3
  • CH₂ CH2 CH3 Terminals represent methyl group

Isomers

• Various representations of 2-bromobutane are:
  • CH3 CH CH CH3
  • CH3CHBrCH₂CH₂ (b) Br (c) Br

Cyclic Compounds

• Bond-line formulas for cyclic compounds
  • Cyclopropane =
  • Cyclopentane =
  • Chlorocyclohexane Cl

Classification of Organic Compounds

• Organic compounds are classified by structures into acyclic/open chain, and cyclic/closed chain compounds

Acyclic Compounds

• Acyclic compounds, also called aliphatic, consist of straight or branched chains
• Ethane, isobutane: For example: CH3CH3, CH3- CH —CH3 CH3

Cyclic Compounds

• Alicyclic (aliphatic cyclic) compounds have carbon atoms joined in a ring

Cyclic Examples

• Cyclopropane
• Cyclohexene
• Cyclohexane

Ring Structures

• Sometimes rings contain atoms other than carbon (heterocyclic)
• Tetrahydrofuran is an example of a heterocyclic compound

Properties

• Tetrahydrofuran exhibits properties similar to aliphatic compounds

Aromatic Compounds

• Aromatic compounds include benzene and related ring compounds (benzenoid)

Heteroatoms

• Like alicyclic compounds, aromatics can have hetero atoms in the ring, called heterocyclic aromatic compounds
  • Examples
    • Benzoid aromatic compounds
      • Benzene
      • Aniline
      • Naphthalene
    • Non-benzenoid compound
      • Tropone

Functional Groups

Functional Group Definition

• A functional group is an atom or group of atoms joined to the carbon chain, responsible for characteristic chemical properties
• Examples: hydroxyl (-OH), aldehyde (-CHO), carboxylic acid (-COOH) groups

Homologous Series

• A series of organic compounds with a characteristic functional group forms a homologous series, where the members are called homologues
• Members have a general molecular formula and differ by a –CH2 unit
• Examples of homologous series: alkanes, alkenes, alkynes, haloalkanes, alkanols, alkanals, alkanones, alkanoic acids, amines

Polyfunctional Compounds

• Compounds can have two or more identical or different functional groups, giving rise to polyfunctional compounds

Nomenclature

• A systematic method of naming organic compounds for clear identification
• Known as the IUPAC (International Union of Pure and Applied Chemistry) system

System Correlation

• IUPAC system names are correlated with structure, so the structure can be deduced from the name
• Before IUPAC, names were based on origin or properties; citric acid is from citrus fruits, formic acid from the Latin word for ant(formica)

Common Names

• Alternative to systematic names (Buckminsterfullerene)
• Useful and indispensable, especially when systematic names are lengthy/complicated
• Table 8.1 has of common names of some organic compounds

IUPAC Nomenclature

• A systematic name of an organic compound is derived by identifying parent hydrocarbon and functional group(s)
  • Functional
    • Branch
      • Parent chain
• OH CH-CH-CH2-CH-CH-CH Br HC H3

Prefixes and Suffixes

• Parent name is modified using prefixes and suffixes to obtain the complete name
• Compounds with only carbon and hydrogen are hydrocarbons

Saturated Hydrocarbons

• Saturated hydrocarbons contain only carbon-carbon single bonds
• IUPAC name for homologous series is alkane
• Unsaturated hydrocarbons have at least one carbon-carbon double or triple bond

Straight-Chain Hydrocarbons

• Names are based on chain with suffix ‘-ane'; prefix indicates number of carbons
• Prefixes derived from trivial names for C1 to C4(methane to butane)
• Alkanes differ by number of -CH₂ groups in the chain so They are homologs

Branched-Chain Hydrocarbons

• Branched chain compounds have small chains (alkyl groups) attached to the parent chain
• The IUPAC names are prefixed to parent alkane
• Alkyl group is a saturated hydrocarbon without one hydrogen atom; methane, C becomes methyl,

Commonly Prefixed

• Commonly prefixed alkyl groups - methyl - ethyl - propyl - butyl - decyl

Abbreviations

-methyl is Me, ethyl is Et, propyl is Pr and butyl is Bu

• Alkyl groups can also be branched, thus requiring appropriate names and positions to represent

IUPAC rules to name branched-chain alkanes

• Longest carbon chain molecules must be identified
• Carbon atoms of the parent chain are numbered for identifying parent alkane/location of carbon atom

Position

• Carbon Atoms - location of carbons where branching occurred due to an alkyl group substitution
• Branched carbon atoms get the lowest possible numbers
• Name of alkyl groups must be put in front of the parent name alkane
• Position and substituents is determined by an appropriate number
• If different alkyl subsitutents is present, list in alphabetical order

Additional

• Methylnonane is an example ([NOTE: numbers are separated by hyphens])
• Substituents is separated by common number called comma
• No repeat of Identical substituents, prefix like di(for 2)

Rules

• Two chains for equal sized, chain for selected contains more sized chains
• Selection, for done close chain for near of chain substitutent

Cyclic Nomenclature

• Prefix ‘cyclo’ + corresponding alkane name for naming saturated monocyclic C
• Use rules for additional chain if present (substituents)

Order of Numbering

• Alphabetical order of numbering

Functional Groups

• Functional groups are atoms or groups of atoms bonded that determine its reactions, earlier definition
• Molecules are usually participate in general for not formation of ions
• One is named for being substrate and other is reagent
• Carbon is general formed with new molecule for bond by substrate

Reactivity Sites

• Reagents attack the reactive site for molecule on atom that it is found
• Reactions with curved - arrows

Inductive effect

• A covalent bond with different electronegativity
• Inductive effects are substituent based on the ability on either for withdrawing or contributing electron

Electronegativity

• halogens and nitro,cyano,carboxyl,ester,aryloxy is electron pulling group usually
• The alkyl methyl and ethyl are commonly donating groups

Resonance Structure

• Benzene structure must have single and double bonds
• It represents the property -- Energetically identical structures I & 2

Rules to Applies

• Structures must have positions of nuclei is the same and same unpaired electrons

Stability

• One must have more bonds, less opposite charges, dispersal of charge and electrons for their octet(8) and exceptions to get that

Resonance effects

• Polarity by transferring 2π to lone pairs on the molecule by atoms for adjacent
• By chain, which are positive effects

Electromeric effect

• Show the effect of an attacking
• Attacking reagent transferred 2π with electrons
• Shifting is done arrow
• In case for when there are functional and electroneg effects for opposite the predominant effects
• The stabilizing of the interaction will affect the atoms

types of reactions and mechanisms

(i)

• Substitution reactions (ii)
• Addition reactions (iii)
• Elimination reactions (iv)
• Rearrangement reactions

Methods for the compound of purification

• Compounds extracted for substance/synthesized will need have method to for being essential/ purified
• This one had common various techniques with (i),Sublimation (ii),Crystallisation (iii),Distillation.. etc

Purity

• A compound had it finally with a purity and ascertained their (melting and/or boiling) point
• A compound could be easily for showing/having new and organic ways to easily clean based.

Explore the unique bonding properties of carbon, including catenation and covalent bonds with various elements. Learn about the historical distinction between organic and inorganic compounds and the pioneering syntheses that disproved the vital force theory. Discover the tetravalence of carbon and its significance in organic chemistry.