Likewise, forensic geneticists can determine whether a crime scene sample of human tissue, such as blood or skin cells, contains DNA that matches exactly the DNA of a suspect. Watch this video animation of how DNA is packaged for a visual lesson in its structure.
Amine functional groups are found in a wide variety of compounds, including natural and synthetic dyes, polymers, vitamins, and medications such as penicillin and codeine. They are also found in many molecules essential to life, such as amino acids, hormones, neurotransmitters, and DNA.
Addictive Alkaloids Since ancient times, plants have been used for medicinal purposes. One class of substances, called alkaloids, found in many of these plants has been isolated and found to contain cyclic molecules with an amine functional group.
These amines are bases. The free compound can be recovered after extraction by reaction with a base: The structures of many naturally occurring alkaloids have profound physiological and psychotropic effects in humans.
Examples of these drugs include nicotine, morphine, codeine, and heroin. The plant produces these substances, collectively called secondary plant compounds, as chemical defenses against the numerous pests that attempt to feed on the plant: In these diagrams, as is common in representing structures of large organic compounds, carbon atoms in the rings and the hydrogen atoms bonded to them have been omitted for clarity.
The solid wedges indicate bonds that extend out of the page. The dashed wedges indicate bonds that extend into the page. Notice that small changes to a part of the molecule change the properties of morphine, codeine, and heroin.
Morphine, a strong narcotic used to relieve pain, contains two hydroxyl functional groups, located at the bottom of the molecule in this structural formula. Changing one of these hydroxyl groups to a methyl ether group forms codeine, a less potent drug used as a local anesthetic. If both hydroxyl groups are converted to esters of acetic acid, the powerfully addictive drug heroin results Figure 3.
Figure 3. Poppies can be used in the production of opium, a plant latex that contains morphine from which other opiates, such as heroin, can be synthesized. Like amines, various nomenclature rules may be used to name amides, but all include use of the class-specific suffix -amide: Amides can be produced when carboxylic acids react with amines or ammonia in a process called amidation.
A water molecule is eliminated from the reaction, and the amide is formed from the remaining pieces of the carboxylic acid and the amine note the similarity to formation of an ester from a carboxylic acid and an alcohol discussed in the previous section : The reaction between amines and carboxylic acids to form amides is biologically important. It is through this reaction that amino acids molecules containing both amine and carboxylic acid substituents link together in a polymer to form proteins.
Proteins and Enzymes Proteins are large biological molecules made up of long chains of smaller molecules called amino acids. Organisms rely on proteins for a variety of functions—proteins transport molecules across cell membranes, replicate DNA, and catalyze metabolic reactions, to name only a few of their functions.
The properties of proteins are functions of the combination of amino acids that compose them and can vary greatly. Amino acids are organic molecules that contain an amine functional group —NH2 , a carboxylic acid functional group —COOH , and a side chain that is specific to each individual amino acid.
Most living things build proteins from the same 20 different amino acids. Amino acids connect by the formation of a peptide bond, which is a covalent bond formed between two amino acids when the carboxylic acid group of one amino acid reacts with the amine group of the other amino acid.
The formation of the bond results in the production of a molecule of water in general, reactions that result in the production of water when two other molecules combine are referred to as condensation reactions. The resulting bond—between the carbonyl group carbon atom and the amine nitrogen atom is called a peptide link or peptide bond. Since each of the original amino acids has an unreacted group one has an unreacted amine and the other an unreacted carboxylic acid , more peptide bonds can form to other amino acids, extending the structure.
Figure 4 A chain of connected amino acids is called a polypeptide. Proteins contain at least one long polypeptide chain. Figure 4. This condensation reaction forms a dipeptide from two amino acids and leads to the formation of water.
Enzymes are large biological molecules, mostly composed of proteins, which are responsible for the thousands of metabolic processes that occur in living organisms. Enzymes are highly specific catalysts; they speed up the rates of certain reactions.
Enzymes function by lowering the activation energy of the reaction they are catalyzing, which can dramatically increase the rate of the reaction. Most reactions catalyzed by enzymes have rates that are millions of times faster than the noncatalyzed version. Like all catalysts, enzymes are not consumed during the reactions that they catalyze.
Enzymes do differ from other catalysts in how specific they are for their substrates the molecules that an enzyme will convert into a different product. Each enzyme is only capable of speeding up one or a few very specific reactions or types of reactions. Since the function of enzymes is so specific, the lack or malfunctioning of an enzyme can lead to serious health consequences.
One disease that is the result of an enzyme malfunction is phenylketonuria. In this disease, the enzyme that catalyzes the first step in the degradation of the amino acid phenylalanine is not functional Figure 5. Untreated, this can lead to an accumulation of phenylalanine, which can lead to intellectual disabilities. Figure 5.
A computer rendering shows the three-dimensional structure of the enzyme phenylalanine hydroxylase. In the disease phenylketonuria, a defect in the shape of phenylalanine hydroxylase causes it to lose its function in breaking down phenylalanine. Kevlar Kevlar Figure 6 is a synthetic polymer made from two monomers 1,4-phenylene-diamine and terephthaloyl chloride Kevlar is a registered trademark of DuPont.
Kevlar is typically spun into ropes or fibers. The material has a high tensile strength-to-weight ratio it is about 5 times stronger than an equal weight of steel , making it useful for many applications from bicycle tires to sails to body armor. Figure 6. This illustration shows the formula for polymeric Kevlar. PCl3, PCl5, oxalyl chloride and a host of other reagents can also work. Alternatively, treating a carboxylic acid with an acyl halide will deliver an anhydride, which can also be effective.
Halides e. So by adding an amine to an acyl halide or acid anhydride, nucleophilic acyl substitution can occur under much milder conditions, resulting in our desired amide. One thing to note with acid halides is that the process generates a single equivalent of HCl as a byproduct.
One way to ensure the reaction proceeds to completion is to add a second equivalent of amine. If you need a refresher on the mechanism of nucleophilic acyl substitution,[ click here and an image of the mechanism will pop up ].
One of the intermediates in this process is a primary amide. Attempts to make this cyclic amide by converting a carboxylic acid to an acyl halide with SOCl2, PCl3, PCl5, and a host of other methods all failed. The active ester is then attacked by the amine in a classic nucleophilic acyl substitution, which leads to the formation of the amide.
Looking at the byproduct, note that there are two hydrogens each attached to nitrogen and an oxygen attached to the central carbon. Since this reaction occurs under neutral conditions, it is extremely useful in the synthesis of peptides, which can undergo racemization epimerization , actually under both basic and acidic conditions.
For a bonus method of amide synthesis, read on. What happens? Amines are bases, and carboxylic acids are, well, acids. Add the two together and you get an innocuous salt. The method is nothing if not direct, and has all the subtlety of a howitzer. However, if one hits this salt with the chemical equivalent of the Hammer of Thor: brute-force, high heat, a series of proton transfers from the ammonium salt can occur.
In certain cases, especially simple amides, and also in the formation of simple lactams, the process can be satisfactory. In many other cases, however, it results in the formation of a black tar at the bottom of your flask from which no useful product may be obtained. As any organic chemist can tell you, there are many diverse ways to create intractable black tars at the bottom of your flask, and this is just one method.
Think of how much you still have to discover! Note 2.Bode, J. Park, Org. This robust and practical method is general for the coupling of various racemization-prone acid substrates and amines, including relatively non-nucleophilic anilines, and provides amides in high yields with very low epimerization. Lanthanum trifluoromethanesulfonate is an avid catalyst for the coupling of setbacks with amides to yield amides under mild boots. Veitch, K. Terada, N.
A photoorganocatalytic reaction of aldehydes with diisopropyl azodicarboxylate leads to an intermediate carbonyl imide, which can react with a variety of amines to afford amides. Chen, J.
Examples of these drugs include nicotine, morphine, codeine, and heroin. Hofmann rearrangement Hofmann rearrangement, also known as Hofmann degradation and not to be confused with Hofmann elimination , is the reaction of a primary amide with a halogen chlorine or bromine in strongly basic sodium or potassium hydroxide aqueous medium, which converts the amide to a primary amine. Tania, J. Okamoto, F.
Noda, J. Kyhl In addition to its better-known uses, Kevlar is also often used in cryogenics for its very low thermal conductivity along with its high strength. Like all catalysts, enzymes are not consumed during the reactions that they catalyze. Deoxo-Fluor is a versatile and mild reagent for acyl fluoride generation and subsequent one-flask amide coupling.
Lee, S. The reaction is compatible with hydroxyl groups and both Fmoc and Boc protecting groups for amines. Yadav, B. The conversion of carboxylic acids to their corresponding acid chlorides occurs rapidly in the presence a tertiary amine base and 3,3-dichlorocyclopropenes via aromatic cation-activated nucleophilic acyl substitution.
Organisms rely on proteins for a variety of functions—proteins transport molecules across cell membranes, replicate DNA, and catalyze metabolic reactions, to name only a few of their functions. Zhang, L. Kumar, V. Enzymes are highly specific catalysts; they speed up the rates of certain reactions. In the presence of sodium acetate, the reaction between 2,2,6-trimethyl-4H-1,3-dioxinone and secondary or tertiary alcohols or primary or secondary amines could be carried out in refluxing tetrahydrofuran. Since the function of enzymes is so specific, the lack or malfunctioning of an enzyme can lead to serious health consequences.
Vishwanatha, V. Gopi, J. Kevlar is typically spun into ropes or fibers. Bombrun, J. Kanno, S.