Organic Compounds

Organic Compound: defined as many compounds that contain covalently-bonded carbon atoms.  They form the basis of life, and are obtained from living sources (i.e. your skin bones and hair.)

Inorganic Compound: compounds other than organic compounds.  There are a few exceptions, however, and they include some compounds and polyatomic ions that contain only one carbon.

The Origins of Organic Chemistry: before 1828, anything that was isolated from animal or plant material was thought to contain a “vital force”.  The study of living things later became called organic chemistry, which was named by Friedrich Wohler, who is also known as the Father of Chemistry.

Fossil Fuels: the products of decomposition of once-living organisms, formed beneath the Earth’s surface by the action of great pressure and high temperatures.  This happens over millions of years.

Properties of the Carbon Atom: it can bond with as many as four other atoms.  It can form many different compounds.  Carbon is able to form rings, chains, spheres, ECT, which is known as catenation.  It can also hold extremely strong bonds.

Hydrocarbons: molecules that are only composed of carbon and hydrogen atoms.  There are two types of them,

1. Aliphatic: open chained or cyclic molecules.

  • Alkanes: contain only carbon-carbon single bonds.
  • Alkenes: contain one or more carbon-carbon double bonds.
  • Alkynes: contain carbon-carbon triple bonds.
  • Alicyckics : special class of aliphatic on which arrangement is cyclic, which means a ring structure.

2. Aromatic: also cyclic, however, some electrons are shared between the carbon atoms in the ring.

Alkanes

Review: alkanes are hydrocarbons that have only single bonds.

Methane (CH4): is the simplest alkane.  At room temperature it is colourless and odourless, and is a major component of natural gas.  Methane is the starting material for many other compounds.  It is produced as a by-product of bacterial decomposition in the absence of air, and is made is waterlogged areas.  The carbon atom is bonded to four hydrogen atoms, which gives the compound a tetrahedral shape.

Tetrahedrons: the geometric structure in which all angles are the same.

Ethane (CH3CH3): the second member of the alkane series.  Also a gas at room temperature, and is a component of natural gas.  The carbon atoms are bonded to three hydrogen atoms, as well as the other carbon atom.  Also has tetrahedral shape.

Propane (C3H8): the third member of the alkane series.  Is usually in liquid state, and is kept in a container with very high pressure for the propane to stay in the liquid state.

Butane (C4H10): component of both natural gas and crude oil.

Constitutional Isomers: formally called structural isomers, and are compounds that have the same molecular formula but different arraignment of the atoms, or have different connectivity, which means are bonded in different orders. There are different types of connections which include;

  • Straight Chain: when each carbon is bonded to a maximum of two other carbons
  • Branched Chain: when one or more carbon atoms in the molecule are bonded to three or four other carbon atoms.

Naming Straight Chain: the IUPAC system uses prefixes to indicate the number of carbon atoms in each chain, (i.e. meth, eth, prop, but, pent ect.)

Naming Branched Chain: first you must identify the parent or base chain, which is the longest continuous chain of carbon. And then name the prefix accordingly.  The side chain to the parent chain is called the substituent.  You name the substituents by counting the number of carbon atoms each substituent contains, and then use the appropriate prefix.  Then add the suffix –yl.

Cycloalkanes: molecules with cyclic structure.  Are named just like straight chained

Alkenes and Alkynes

Unsaturated Compound: any organic compound that contains at least one double or triple bond between its carbon atoms. i.e. alkenes and alkynes.

Saturated Compound: an organic compound that contains a single bond between carbon atoms. i.e. alkanes.

Ethene (C2H4): the simplest alkene, more commonly known as ethylene.  It is used to produce plastics, and is also important in the agricultural industry.

Naming Alkenes: similar to alkanes, except when identifying the parent hydrocarbon, you must choose the carbon chain that contains both carbon atoms of the double bond, even if it is not the longest.  The double bond is indicated by the ending of -ene.  If there are more than three carbon atoms in the parent chain, and number must be used to indicate where the double bond starts.  If two double bonds are present, ending -diene is used.

Positional Isomers: isomers of organic molecules that have the same carbon skeleton but differ in the position of the multiple bonds.

Geometric Isomers: type of stereoisomer, also called cis-trans isomers.

Stereoisomer: any two or more compounds that have their atoms connected in the same order but have different three dimensional arrangements.

Ethyne (C2H2): the simplest alkyne, also known as acetylene.  Is a colourless gas that is used in household lighting and batteries.

Homologous Series: the compounds ethyne, propyne, 1-butyne, and 2-butyne are the first members of this series.  Since alkynes always contain triple bonds they form homologous series.  They have four characteristics;

  • All members differ by a simple repeating unit. i.e. CH4, C2H6 , C3H
  • All can be represented by a  general formula of CnH2n+2, the alkenes follow CnH2n and the alkynes are CnH2n-2
  • All members exhibit similar chemical properties
  • All members exhibit a gradual change in physical properties, i.e. the size and molar mass increase.

Naming Alkynes: similar to alkenes except the use of ending –yne is used to show the presence of a triple bond. First identify the longest chain with the triple bond, and count the number of carbon atoms.  Then number the long chain and say the number for where the triple bond is.  Then number and name substituents.

Properties of Hydrocarbons

Physical Properties: refers to those such as boiling point, melting point, solubility and density.

  • Boiling Point: for straight line chain, increases with the number of carbon atoms.  And in general, branched chains of alkanes have lower bowling points.
  • Melting Point: generally increases as the mass and length of the chain increase.  Alkanes with even numbers of atoms tend to have slightly higher melting points than those with odd numbers.
  • Density: the higher the intermolecular forces, the greater the density.  They generally have low density, even lower then water.
  • Solubility: since hydrocarbons are non-polar, they are not soluble in water and other polar solvents.

Chemical Properties: hydrocarbons are used as raw material for making many new molecules.

  • Combustion Reactions: all hydrocarbons are combustible, meaning that they burn.  If there is excess oxygen then combustion can occur.
  • Substitution Reactions: because of the closeness of the bond between hydrogen and carbon they are very unreactive.  Reactions usually require additional energy.
  • Addition Reactions: the ones with double or triple bonds however, are more reactive than the alkanes.  They participate in addition reactions, in which a

multiple bond is converted to a single bond.

AlkanesC-C, single bondUnreactive at ordinary temp, due saturation
AlkenesC C, double bondAddition required due to presence of C C
AlkynesC C, triple bondAddition required to presence of C C
  • Polymerization Reactions: a polymer is a large organic molecule that consists of many identical units, and polymerization is a reaction that makes polymers.

Petrochemicals

Petrochemicals: are organic compounds found in or revived from petroleum(crude oil) and is used in the production of products other than fuels.

Polythene: the simplest polymer from ethene.  There  are two types of polythene, that  of which are plastics that harden when cooled, but soften again when heated (thermoplastic).  Low-density polythenes are used for plastic bags, food wrap, ect.  And high-density is used for chairs, tables ect.

Polypropene: the simplest polymer made from propene.  Used for very strong products.

Energy and Bonds

  • Energy: the ability to work or the capacity to produce change.
  • Heat: the flow of thermal energy from a warmer object to a cooler one.
  • Temperature: the measure of the average thermal energy of a substance.
  • Thermochemistry: the study of heat changes associated with chemical reactions, and is a part of thermodynamics.
  • Joule: SI unit for measuring energy.
  • Law of Conservation of Energy: theory that states that energy can neither be created nor destroyed.  In other words, energy can be converted from one form to another with no net loss or gain.
  • Energy Change: in a chemical reaction the difference between the energy required to break chemical bonds in the reactant, and the energy released by the formation of the bonds in the products.
  • Endothermic: reaction that absorbs heat from the surroundings.
  • Exothermic: reaction that releases heat to the surroundings.
  • Predicting Energy Change: it is important to have as much information as possible when doing experiments, and knowing whether the reaction will be endothermic or exothermic is very useful.  Depending on the type of bond, i.e. single, double ect., the energy changes, and as the bond changes from single to double, the amount of energy increases.
  • Thermochemical Reaction: a chemical equation in which the heat of reaction is included.

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