Lesson 9 - Saturated Hydrocarbons PDF

Alkanes Understanding Saturated Hydrocarbons By Solav Salih Medicine (Pathway Programme) Chemistry Module 2024-2025  Learning points Discuss the significance Understand the Underst...

Alkanes Understanding Saturated Hydrocarbons By Solav Salih Medicine (Pathway Programme) Chemistry Module 2024-2025  Learning points Discuss the significance Understand the Understand and explain and applications of classification of organic the structure, saturated hydrocarbons compounds into saturated properties, and in various industries, and unsaturated nomenclature of including fuels and hydrocarbons saturated hydrocarbons petrochemicals.  Introduction to Organism Organic Chemistry Organic chemistry is the study of carbon- containing compounds Berzelius In 1807 Berzelius introduced the word “Organic” to describe molecules formed by living or once living organisms. In 1828 Friedrich Wöhler, the “father of organic chemistry”, synthesized the first organic Urea molecule urea. Wöhler  Classification of hydrocarbons Saturated Unsaturated Functional groups An atom or group of atoms Responsible for the chemical and physical properties of the molecule They replace a hydrogen atom and form a substituted hydrocarbon What are alkanes? Alkanes are saturated hydrocarbons Contain only single bonds. is the general formula Name: prefix (related to the number of carbons) + ane Linear, branched, or cyclic Alkyl groups A type of substituent derived from an alkane by removing one hydrogen atom. The -ane ending of the alkane name is replaced by the -yl ending. Bonds to hydrocarbon chains to form branched chains. Nonpolar atom Nonpolar atom Alkane Physical properties Symmetrical distribution of electrons Nonpolar molecules Low melting and boiling points Main intermolecular forces are weak London dispersion forces short-lived dipoles form because the electrons are in constant motion At room temperature: 1-4 carbons -> gaseous 5-17 carbons -> colourless liquid >18 carbons -> white, waxy solids Induces dipole moment in neighboring atom  Alkane Physical properties Larger molecular mass --> more electrons --> stronger attraction --> higher boiling and melting points Branched-chain hydrocarbons --> smaller surface area than their straight-chain isomers --> weaker London dispersion forces --> lower melting and boiling points.  Chemical formulas in organic chemistry Molecular formula Does not show the bonding pattern Structural formula Too bulky for large molecules  Chemical formulas in organic chemistry Condensed formula Line formula The simplest representation of a molecule  Practice Draw the structural and condensed formulas of this molecule. problem  IUPAC nomenclature 1. Name the longest continuous carbon chain 2. Number the parent chain to give the lowest number to the carbon bonded to the first group 3. Add the number and name of the substituents before the parent compound’s in alphabetical order Practice problem: Can you name the above structures? Practice problem: a) 2,3-Dimethylpentane b) 1,2-Dibromo-3-chlorobutane Draw the structural formula from the compounds’ IUPAC names.  Constitutional or Structural Isomers Same molecular formula, different arrangement of atoms They have different physical and chemical properties Branched chains --> lower boiling points Practice problem: write all the constitutional isomers having the molecular formula C6H14.  Cycloalkanes Carbon-carbon single bonds in a ring structure. 2 fewer hydrogen atoms Name? than their corresponding alkane: Name: [cyclo-] + name of Name? the alkane  Stereoisomers Same structural formulas and bonding patterns but differ in the orientation of their atoms in space Cis-trans isomers, or geometric isomers: forms when there is absence of free rotation, such as in cyclic structures. The arrangement of substituents in space can differ, resulting in the cis- and trans- isomers. cis-1,2-dimethylcyclohexane trans-1,2-dimethylcyclohexane Reactions of Alkanes and Cycloalkanes Combustion Burning hydrocarbons at high temperatures in the presence of excess oxygen will produce carbon dioxide, water vapor, and release large amounts of energy as heat. Hydrocarbons as fuel Combustion is the process by which we heat our homes, run our cars, and generate electricity Large amount of energy, availability and relatively low cost Effect on Environment CO2 is Earth's most important greenhouse gas The buildup of CO2 from fossil fuel burning will trap heat and lead to a rise in earth’s temperature, which is global warming  Incomlete Combustion Without a sufficient supply of oxygen, incomplete combustion occurs. for example: Carbon monoxide poisoning Blue Flame Yellow/Red Flame Result of complete combustion Result of incomplete combustion More heat energy Lower temperature Cleaner Produces soot Reactions of Alkanes and Cycloalkanes Halogenation A substitution reaction where a halogen substitutes a hydrogen in the alkane Produces an alkyl halide and a hydrogen halide Occurs only in the presence of heat and/or light Alkyl halides act as solvents, insecticides, and herbicides. Useful reactants for the synthesis of other organic compounds