What is Organic?
Table of contents
"Organic" is generally associated the word with organic foods and products, but in the sciences, organic chemistry is refered to as the study of carbon compounds.
What do people think organic is? A survey was conducted to ask participants about what they thought organic meant. Most of the replies referred to organic foods, while only a few science majors said carbon compounds. Organic chemistry is the study of the structure, properties, and reactions of carbon compounds. Even though organic chemistry focuses on carbon, many organic compounds can contain hydrogen, nitrogen, oxygen, phosphorous or other elements. Carbon molecules have many different functions; they are commonly used in medicine, food, paints, and gasoline.
|Number of Carbon(s): ||Prefix: ||Number of Carbon(s):||Prefix:|
See Nomenclature for Organic Chemistry for more information on how to properly name organic molecules.
A trick to remember the prefixes of Met-, Eth-, Prop-, and But- is: Monkeys Eat Pink (or Plenty) Bananas.
The simplest type of hydrocarbons are called alkanes which consist only of single bonded atoms with a molecular formula of CnH2n+2 where n is equal to the number of carbons. They are named using the prefixes above, and by adding the suffix, "-ane."
- CH4 - Methane
- C2H6 - Ethane
- C3H8 - Propane
- C4H10 - Butane
Other kinds of hydrocarbons include: alkenes and alkynes. Alkenes are carbon compounds with at least 1 double bond between 2 carbon atoms, with the molecular formula CnH2n. They are named by adding the suffix, "-ene" to the prefix based on the number of carbons.
- C2H4 - Ethene
- C3H6 - Propene
- C4H8 - Butene
Alkynes are carbon compounds with one triple bond between two carbon atoms and are expressed with the molecular formula, CnH2n-2. They are named by adding the suffix, "-yne" to the prefix based on the number of carbons.
- C2H2 - Ethyne
- C3H4 - Propyne
- C4H6 - Butyne
Naming Alkyl Compounds
Alkanes are often present as alkyl substituents (alkyl groups) that attach to other groups in larger organic molecules. Their molecular formulas have one less hydrogen than a normal alkane. They are named by replacing the normal alkane ending "-ane" with "-yl." The letter "R" commonly refers to any alkyl functional group.
- CH3- methyl
- CH3CH2- ethyl
- CH3CH2CH2CH2- butyl
- R- any alkyl group
Examples of compounds with alkyl groups:
CH3I: methyl iodide CH3CH2OH: ethyl alcohol CH3CH2CH2NH2: propylamine R-O-R: an ether
CH3NH2: methylamine CH3CH2OCH3: ethyl methyl ether CH3CH2CH2CH2Cl: butyl chloride R-NH2: an amine
Note that when there are two or more alkyl groups present, as in an ether, they must be stated in alphabetical order.
Structures of Organic Compounds
consists of a hydrocarbons chain that has a hydroxide in place of hydrogen (anywhere in the compound). The common formula for an alcohol is R-OH, where R is any hydrocarbon (residue group). Naming alcohols is not hard either; for example propanol which comes from the propane hydrocarbon therefore instead of having the –ane suffix you have –anol. Other examples are ethanol, butanol, Alcohols have the ability of making acids solutions. A common reaction of alcohols is with carboxylic acids to make water and an ester.
consists of two hydrocarbons joined by a oxygen between the them. Naming theses two compounds is as easy as naming the two alkyl groups (in alphabetical order) and ether at the end. An example is ethyl ether propyl, the structural formula is CH3CH2OCH2CH2CH3. Another example is ethyl ethyl ether more commonly named as diethyl ether. The common formula for ethers is R-O-R, this means there are two alkyl groups (aka residue groups).
consists of an alkyl group missing three hydrogen that were replaced by double bonded oxygen and a hydroxide group. The common formula for carboxylic acids is R-COOH. Naming carboxylic acids is not hard, starting with propane and replaces the suffix –ane with -anoic acid, this compound is propanoic acid and has the structural formula of CH3CH2COOH. Some characteristics of this compound are reacting with alcohols to form water and an ester. Carboxylic acids also have a similar property to that of alcohols; both alcohols and carboxylic acids form weak acidic solutions in water.
are generally formed through the reaction of carboxylic acids and alcohols. Esters are the reason why certain foods have certain scents; this makes the useful with perfumes. The general formula for an ester is R-COOR; naming esters is a little harder than naming other compounds but basically the alcohol gets the alkyl name ending and the carboxylic acid gets the –anoate i.e. methanol reacting with butanoic acid to make water and methyl butanoate; structural formula being CH3COOCH2CH2CH2CH3.
have the general formula R-CHO. Naming these compounds should not be confused with alcohols; aldehydes have the –al suffix while alcohols have the –ol suffix. For example methanal (aka formaldehyde) is the simplest aldehyde.
have the general formula R-COR and contain the suffix –one. An example of a ketone is butanone also know as methyl ethyl ketone to distinguish where the oxygen is located. Other was of identifying the location of the oxygen is by naming each carbon numerically and adding the number of the carbon, where the oxygen is found, to the formula, such as 2-butanone.
are essentially hydrocarbons where hydrogens have been replaced by halogens. When the halogens are in the compound you change the name, fluorine to fluoro, chlorine to chloro, bromine to bromo, and iodine to iodo. An example of this compound is 2-choloropropane, CH3CHClCH3. Like ketones, you should denote where the halogen is located in the compound by numbering the carbons in the compound.
contain a nitrogenous base and have the structural formula R-NH2. These compounds have the ability of making weak basic solutions by attracting hydrogen to form A R-NH3+. Naming this compounds just requires the addition of the suffix –amine after the alkyl name i.e. methylamine, CH3NH2.
Cycloalkanes are alkanes that have ring, or cyclic structures. They have the molecular formula CnH2n. Because the atoms are arranged in a ring shape, the bond angles are less than they would be in ideal sp3 carbon. This is referred to as ring strain. As a result of ring strain, the bond energies of cycloalkanes are much less than those of regular alkanes. In order to avoid ring strain, cycloalkanes in nature are often found in different conformations. One example is the chair conformation of cyclohexane.
Cyclohexane, C6H12, is a cycloalkane with 6 carbons.
Cyclohexane is rarely found in its ring structure though because of its ring strain. More often it is found in a chair conformation. The bond angles in the chair conformer are very close to the ideal bond angles of sp3 carbons. About 110.9o compared to 109.5o (25) which is why this conformation is more stable than the ring structure.
Benzene is a very important organic compound that is commonly used in manufacturing and as an organic solvent in labs. Its molecular formula is C6H6. In your organic chemistry textbook, you may see it presented in a ring structure:
It may be confusing as to how these "lines" can be a molecular structure. This notation is a quick method for chemists to draw organic molecules because the molecules can be very complex. In every corner, there is a carbon, bonded to hydrogen because carbon likes to make 4 bonds.
This is what the above structures of benzene actually represent:
Isomers and Stereochemistry
The structures of organic molecules are very important in considering their properties. Most organic molecules display geometric properties such as isomerism. Isomers are compounds with identical molecular formulas, but with different structures. There are 2 kinds of isomers: constitutional isomers and stereoisomers. Constitutional isomers differ in the connectivity of their atoms. Stereoisomers are compounds that maintain the same connectivity, but differ in the way their atoms are spatially arranged. There are 2 kinds of stereoismers: cis-trans isomers and enantiomers. Cis-trans isomers have different orientations of their functional groups. In a cis isomer, the highest priority functional groups are located on the same side of the double bond. In a trans isomer, the highest priority functional groups are located on opposite sides of the double bond. Enantiomers are compounds that have nonsuperimposable mirror images of each. A molecule or object that has a nonsuperimposable mirror image is chiral.
Constitutional Isomers: CH3CH2OH and CH3OCH3
Chirality and Enantiomers
In organic chemistry, the concept of chirality is often applied in medicine or compounds because the D-Dopa and the L-Dopa have different functions, one of them does the desired function, while the other one does not. This is because many biological receptor proteins in the body are shaped so that only one enantiomer can bind to the substrate, while the other cannot fit. An example is sugar in biological systems, sugar is preferred in the D-Dopa form because in biological system, amino acids is preferred in the L-Dopa. The mirror images of the molecules does not have the same function as the other, they are usually called chiral. The two chiral molecules are called enantiomers. Non-chiral molecules are molecules that have a plane of symmetry in them and they are called achiral.
- McMurry, John. Organic Chemistry Fourth Edition. Pacific Grove, CA: Brooks/Cole Publishing Company, 1995.
- Bruice, Paula Y. Essential Organic Chemistry. 2nd. Upper Saddle River, NJ: Prentice Hall, 2010.
- A time line of Organic Chemistry: http://www.google.com/search?q=history+behind+organic+chemistry&hl=en&client=firefox-a&hs=0gO&sa=X&rls=org.mozilla:en-US:official&prmd=b&tbs=tl:1&tbo=u&ei=m4H3S52WFI2KNODNiMwF&oi=timeline_result&ct=title&resnum=11&ved=0CFgQ5wIwCg
- Here is an introductory lecture explaining what is organic chemistry: http://www.youtube.com/watch?v=ndOwa5zET8Y&playnext_from=TL&videos=ITH6Tlk20rc
- These songs may also be helpful:http://www.youtube.com/watch?v=DXa2QDQzwzM&playnext_from=TL&videos=Q_Z_n2SHhBk http://www.youtube.com/watch?v=mAjrnZ-znkY&playnext_from=TL&videos=0pKprCP_0Wk
- Give examples of the different structures carbon can form.
- What are organic molecules?
- What are Hydrocarbons?
- What is the difference between alkanes, alkenes, and alkynes?
- Give at least 2 examples of alkanes, alkenes, and alkynes.
- Carbon is able to form structures such as tubes, spheres, chains, and rings.
- Organic molecules come from living organisms, such as proteins and carbohydrates.
- Hydrocarbons are compounds with hydrogen and carbon; they are usually called the simplest organic compound.
- The differences between alkanes, alkenes, and alkynes are: (Shown in table)
- Examples: (Shown in table - There are multiple correct answers!)
|Single bonded carbon and hydrogen compounds.||Double bonded carbon and hydrogen compounds.||Triple bonded carbon and hydrogen compounds.|
|(Example) Propane, Nonane||(Example) Decene, Hexene||(Example) Butyne, Heptyne|
- Sharon Wei (UCD)
- Jason Ip (UCD)
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