Hydrocarbon Derivatives

HYDROCARBON DERIVATIVES

Not all atomic combinations possible on paper can actually occur in nature. One of the most important jobs of the organic chemist is to synthesize compounds which have been predicted theoretically.

Many compounds that occur in nature have not been classified and analyzed. Another job of the organic chemist is to isolate and analyze natural organic substances. If the chemist can find the structure of a natural compound, he can then attempt to synthesize the material in the laboratory.

We have already seen how complex such jobs can be, even when carbon and hydrogen are the only elements with which the chemist is concerned. When atoms of other elements are introduced into hydrocarbon molecules, literally hundreds of thousands of organic compounds can be (and are) formed.

-Organic compounds are divided into two main classes: hydrocarbons and hydrocarbon derivatives
-Hydrocarbon derivatives are molecular compounds of carbon and at least one other element that is not hydrogen
-Organic halides are organic compounds in which one or more hydrogen atoms have been replaced by halogen atoms
-Common organic halides include freons (chlorofluorocarbons) and Teflon (polytetrafluoroethylene)
-Naming halides uses the same format as branched-chain hydrocarbons
-The branch is named by shortening the halogen name to fluoro-, chloro-, bromo-, or iodo-
-In drawing organic halides using IUPAC names, draw the parent chain and add branches at locations specified in the name
eg.

    Cl Cl
     | |
   H-C-C-H
     | |
     H H


1,2-dichloroethane

-Organic halides react fast which is explained from the idea that no strong covalent bond is broken – the electron rearrangement does not involve separation of the carbon atoms
-Addition of halogens could be added to alkynes which results in alkenes or alkanes
-By adding halogens to alkenes, the product could undergo another addition step, by adding halogens to the parent chain, the double bond has to become a single bond in order to accommodate the halogens
eg.

 Br Br              Br Br
  | |                | |
H-C=C-H + Br-Br => H-C-C-H
         | |
                    Br Br

-By adding hydrogen halides to unsaturated compounds will produce isomers

  H H H               H H H                    H H H
  | | |               | | |                    | | |
H-C=C-C-H + H-Cl => H-C-C-C-H       OR       H-C-C-C-H  
      |               | | |                    | | |
      H              Cl H H                    HCl H

-Substitution reaction is a reaction that involves the breaking of a carbon-hydrogen bond in an alkane or aromatic ring and the replacement of the hydrogen atom with another atom or group of atoms
-With light energy it enables the substitution reaction to move at a noticeable rate eg. C₃H₈ + BR₂ + light => C₃H₇Br + HBR
-Through substitution reaction, in order to name the reaction product, just indicate the location number of the replacement, followed by the halogen prefix (eg. Bromo-) and then state the type of parent chain. Also indicate the second product created from substitution reaction (hydrogen bromide) eg. propane + bromine => 1-bromopropane + hydrogen bromide
-Elimination is an organic reaction in which an alkyl halide reacts with hydroxide ion to produce an alkene by removing a hydrogen and halide ion from the molecule

  H H H             H H H
  | | |             | | | 
H-C-C-C-H + OH => H-C=C-C-H + H-O + Br
  | | |                 |       |
  H BrH                 H       H

-Alcohols have properties that can be explained by the presence of a hydroxyl (-OH) functional group attached to a hydrocarbon chain

-Short-chain alcohols are very soluble in water because they form hydrogen bonds with water molecules

-Alcohols are used as solvents in organic reactions because they are effective for both polar and non-polar compounds

-To name alcohols, the –e is dropped from the end of the alkane name and is replaced with –ol eg. Methane => methanol

-Methanol is also called wood alcohol because it was once made by heating wood shavings in the absence of air

-These days, methanol is prepared by combining carbon monoxide and hydrogen at high temperatures and pressure with the use of a catalyst

-Methanol, however, is poisonous to humans. Consuming a small amount could cause blindness or death

-When naming alcohols with more than two carbon atoms, the position of the hydroxyl group is indicated

-Alcohols that contain more than one hydroxyl group are called polyalcohols, their names indicate the positions of the hydroxyl groups eg. 1,2-ethanediol

-Alcohols undergo elimination reactions to produce alkenes through being catalyzed by concentrated sulfuric acid, which removes or eliminates a hydrogen atom and a hydroxyl group

  H H                  H H 
  | |                  | |
H-C-C-H  + acid  =>  H-C=C-H   +   H-O
  | |                                |
  H OH                               H


ethanol + acid => ethene   + water

-Ethers is a family of organic compounds that contain an oxygen atom bonded between two hydrocarbon groups, and have the general formula R₁-O-R₂

-To name ethers add oxy to the prefix for the smaller hydrocarbon group and join it to the alkane name of the larger hydrocarbon group

eg.

CH3-O-C2H5  


methoxyethane

-Ethers have low solubility in water, low boiling points, and have no evidence of hydrogen bonding

-Ethers undergo chemical change only when treated with powerful reagents under vigorous conditions

-Ethers are formed by the condensation reaction of alcohols

-Condensation reaction is the joining of two molecules and the elimination of a small molecule, usually water

-The carbonyl functional group, -CO-, consists of a carbon atom with a double covalent bond to an oxygen atom

-Aldehydes has the carbonyl group on the terminal carbon atom of a chain

-To name aldehydes, replace the final –e of the name of the corresponding alkane with the suffix –al

-Small aldehyde molecules have sharp, irritating odors whereas larger molecules have flowery odors and is used to make perfumes

-A ketone has the carbonyl group present anywhere in a carbon chain except at the end of the chain

-The difference in position of the carbonyl group affects the chemical reactivity, and enables us to distinguish aldehydes from ketones empirically

-To name ketones, replace the –e ending of the name of the corresponding alkane with –one

-The simplest ketone is acetone (propanone), CH₃COCH₃

-The family of organic compounds, carboxylic acids contain the carboxyl functional group, -COOH, which includes both the carbonyl and hydroxyl groups

-Carboxylic acids are found in citrus fruits, and other foods with properties of having a sour taste

-Carboxylic acids also have distinctive odors (like sweat from a person’s feet)

-The molecules of carboxylic acids are polar and form hydrogen bonds both with each other and with water molecules

-Carboxylic acids acid properties, so a litmus test can separate these compounds from other hydrocarbon derivatives

-To name carboxylic acids, replace the –e ending of the alkane name with –oic, followed by the word “acid”

-Methanoic acid, HCOOH, is the first member of the carboxylic acid family

-Some acids contain two or three carbonyl groups such as oxalic acid, and citric acid

 
    COOH  CH2-COOH
    |   |
    COOH             HO-C-COOH
   |
   CH2-COOH

     

oxalic acid      citric acid

-When carboxylic acids undergo a condensation reaction, in which a carboxylic acid combines with another reactant, it forms two products – an organic compound and water

-Esterification is the condensation reaction in which a carboxylic acid reacts with an alcohol to produce ester and water

-carboxylic acid + alcohol => ester + water

-The ester functional group is similar to that of an acid, except that the hydrogen atom of the carboxyl group is replaced by a hydrocarbon branch

-Esters are responsible for the odors of fruits and flowers and are also added to foods for aroma and taste

-To name an ester, determine name of the alkyl group from the alcohol used in the esterification reaction

-Next change the ending of the acid name from “–oic acid” to “–oate”

-ethanoic acid + methanol => methyl ethanoate + water

-Artificial flavorings are made by mixing synthetic esters to give similar odors of the natural substance

-An amide consists of a carboxyl group bonded to a nitrogen atom

-Amides could be formed in condensation reactions

-Amides occur in proteins, the large molecules found in all living organisms

-Peptide bonds is the joining of amino acids together in proteins

-To name amides, have the name of the alkane with the same number of carbon atoms, with the final –e replaced by the suffix –amide

-Change the suffix of the carboxylic acid from “–oic acid” to –amide to have the same name results eg. ethanamide

-Amines consist of one or more hydrocarbon groups bonded to a nitrogen atom

-Through X-Ray diffraction reveals that the amine functional group is a nitrogen atom bonded by single covalent bonds to one, two, or three carbon atoms

-Amines are polar substances that re extremely soluble in water as they form strong hydrogen bonds both to each other and to water

-Amines have peculiar, horrible odors (eg. smell of rotting fish)

-The name of amines include the names of the alkyl groups attached to the nitrogen atom, followed by the suffix –amine eg. methylamine

-Amines with one, two, or three hydrocarbon groups attached to the central nitrogen atom are referred to as primary, secondary, and tertiary

-Primary amines is when a hydrogen atom attached to the nitrogen atom is replaced by a hydrocarbon group

-Secondary amines are when two hydrocarbon groups replaces the hydrogen atoms and tertiary amines replaces all of the hydrogen atoms with hydrocarbon groups

-Amines are used in the synthesis of medicines

-A group of amines found in many plants are called alkaloids

-Many alkaloids influence the function of the central nervous systems of animals

-Substitution – alkane/aromatic + halogen + light => organic halide + hydrogen halide

-Elimination – alkyl halide + OH => alkene + water |+ water + halide ion

-Elimination – alcohol + acid => alkene + water