By: Sarah Russell and Edward Moore Organic halides
What are organic halides? • Organic halides are organic compounds that contain one or more halogen atoms. • In a hydrocarbon, one or more hydrogen atoms are replaced by halide atoms (fluorine, chlorine, bromine, iodine, astatine) • Also known as Halocarbons or Alkyl Halides.
General formula: CnH2n+1X, where C represents the carbon atoms, H represents the hydrogen atoms, and X represents the halide. • Also represented as R-X, where R=alkyl group, X=halogen substituent. 1,2-dichloroethane http://en.wikipedia.org/wiki/1,2-Dichloroethane
Physical Properties • Bond strength decreases with an increase in the size of the halogen attached (the size of the p orbital increases). This also causes the bond to be longer. • Boiling points are higher then alkanes. Increase with increasing chain length (containing the same halogen) • Little solubility in water, but good solubility in nonpolar solvents.
Naming • Same format as branched chain hydrocarbons. • 1. Identify and name the parent chain (longest) of Carbons. • 2. Identify and name the halogen substituent(s) (remember to use lowest possible numbers). • 3.List substituents in alphabetical order with prefixes.
Note: the halogen branch is named by shortening (fluoro, chloro, bromo, etc.) • 4. Write the IUPAC name of the compound. 1.Parent chain: 4 (saturated) = BUTANE 2.Halogen substituent: 1-Bromine = 1-BROMO 3.1-bromo + butane 4.1-bromobutane (or just bromobutane) http://science.pc.athabascau.ca/reagentstud.nsf/c982974ea911edc887257093006b238d/ee1bb4eb15b5e248872570b2007751b0?OpenDocument Condensed structural formula: CH3-CH2-CH2-CH2-Br
http://www.lookchem.com/cas-471/471-43-2.html 1.Parent chain: 2 (saturated): ETHANE 2.Halogen substituent: 1,1-Flourine=FLUORO, 2,2-Chlorine=CHLORO 3.2,2-Dichloro-1,1-Difluoro + Ethane 4.2,2-dichloro-1,1-difluoroethane
Drawing structural formula • 1. Draw the parent chain of Carbons • 2. Add the position and symbol for each halogen atom • 3. Add the remaining Hydrogen atoms (Carbon forms four covalent bonds because it has 4 electrons)
1,3-dichloropropane Parent chain of Carbon: “PROPANE” = 3 Carbon (saturated) C – C – C 2. Position 1 and 3= DI (2), CHLORO = chlorine C – C – C | | Cl Cl Add Hydrogen (each Carbon need 4 bonds) H HH | | | H – C – C – C – H | | | Cl H Cl
Reactions • 2 main reactions that result in the formation of organic halides: Substitution and Addition. • Difference between the 2 is the hydrocarbons involved.
Addition reactions • Reaction in which substituents are added to both carbons that share a multiple bond. • Similar to “Hydrogenation”, because instead of Hydrogen, a halide is added to an unsaturated hydrocarbon and makes it saturated. • Rapid rate of reaction because no strong covalent bond is broken, no separation of carbon atoms.
H H | | H-C-C-H | | Cl-Cl H H | | H-C=C-H + Cl-Cl Ethene + Chlorine 1,2-dichloroethane As seen here, chlorine is being added to ethene, an unsaturated hydrocarbon, which produces 1,2-dichloroethane, a saturated hydrocarbon. Indicated by the arrows, Chlorine is being added to the new product, but for this to happen the double bond in Ethene is broken up making it Ethane. This process allows the electrons involved in the double bond to be freed so that the chlorine atoms can attach.
Br Br | | H-C=C-H + H-C≡C-H Br-Br Ethyne + Bromine 1,2-dibromoethene As seen here, bromine is being added to ethyne, an alkyne, which produces 1,2-dibromoethene, an alkene. Indicated by the arrows, Bromine is being added to the new product, but for this to happen the triple bond in Ethyne is broken up making it Ethene. This process allows the electrons involved in the triple bond to be freed so that the bromine atoms can attach.
Substitution reactions • Occurs when a hydrogen atom is removed from a hydrocarbon and replaced by a halide. • The breaking of a carbon-hydrogen bond in an alkane or aromatic ring produces an organic halide and a hydrogen halide. • Slow reaction at room temp. (very few molecules that collide are energetic enough to break C-H bonds.
H | H-C-H | H H | H-C-Br | H + Br-Br H-Br + Methane + Bromine Hydrogen Bromide + Bromomethane In this reaction, Bromine is added to Methane to produce Hydrogen Bromide and Bromomethane. As a substitution reaction, a hydrogen atom must be removed from a hydrocarbon and replaced my a halide. One hydrogen on Methane is replaced by a Bromine atom to produce Bromomethane. The left over product of this reaction is a hydrogen atom and a bromine atom, which make Hydrogen Bromide.
H H H | | | H-C-C-C-Cl | | | H HH H H H | | | H-C-C-C-H | | | H H H + Cl-Cl H-Cl + OR H HH | | | H-C-C-C-H | | | H Cl H Proane + Chlorine Hydrogen Chloride + 1-Chloroproane OR 2-Chloroprpane In this reaction, Chlorine is added to Propane to produce Hydrogen Chloride and 1-Chloropropane OR 2-Chloropropane . As a substitution reaction, a hydrogen atom must be removed from a hydrocarbon and replaced my a halide. One hydrogen on Propane is replaced by a Chloride atom to produce 1-Chloropropane OR 2-Chloropropane. The left over product of this reaction is a hydrogen atom and a chlorine atom, which make Hydrogen Chloride. This reaction does produce an isomer because Propane can Chlorine can replace the hydrogen atoms in position 1 and 2.
Elimination Reactions • There is also a third type of reaction involving organic halides, elimination reactions. • Elimination reactions are almost like the opposite of addition reactions. Instead of adding halogens to a hydrocarbon to create an organic halide, halide atoms can be removed from an organic halide with a base to produce an unsaturated hydrocarbon.
H HHH | | | | H-C=C-C-C-H | | H H H H H H | | | | H-C-C-C-C-H | | | | H Cl H H + + + Cl ̄ H2O OH ̄ OR H HHH | | | | H-C-C=C-C-H | | H H 2-chlorobutane + hydroxide 1-butene + chlorine + water 2-butene This is an example of an elimination reaction, where a base is added to an organic halide to produce an unsaturated hydrocarbon and a halide. Here, the base which is Hydroxide, breaks up the organic halide, 2-chlorobutane. This produces the hydrocarbon of either 1-butene or 2-butene, because the halogen atom, chlorine, has been removed which produces a chlorine ion also. Water is also produced because 2 hydrogen atoms are sacrificed to make a double bond in the hydrocarbon and the oxygen from hydroxide is left over.
Everyday use • Freons (chlorofluorocarbons) are used in refrigerators and air conditioners • Teflon (polytetraf) in cookware • Many are toxic (carcinogenics) • DDT (dichlorodiphenyltrichloroethane), insecticide. • PCB’s, (polychlorinated biphenyls) used in electrical transformers
http://www.benbest.com/cryonics/s21cm99.html http://www.lenntech.com/teflon.htm http://www.jrank.org/health/pages/15856/dichlorodiphenyltrichloroethane-(DDT).html http://www.axysanalytical.com/services/organochlorine_legacy_compounds/pcb_polychlorinated_biphenyls/
Fire retardation • Anaesthesia • Plastics manufacturing http://www.diytrade.com/china/4/products/7291276/Alcopanel_FR__Aluminium_Composite_Panel_Fire_Retardation_Grade.html http://news.bbc.co.uk/2/hi/health/7468753.stm http://inhabitat.com/scientists-develop-plastic-producing-bacteria/