Tattoo - ester group

Epoxide group

An epoxide is a functional group derived from the ether group. In fact, it is a cyclic ether, forming a ring with 3 members (2 carbons and 1 oxygen). The cyclic structure is an equilateral triangle and presents a high rigidity and structural tension.

In biochemistry, epoxides are important molecules in many metabolic processes, such as, for example, in the synthesis of cholesterol.

Thioester group

The thioester group, as its name indicates, is characterized by being derived from an ester group, in which the oxygen that is connected by a single bond to the carbon is replaced by a sulfur atom. Its chemical formula is COSR. Thioesters are obtained when a carboxylic acid reacts with a thiol.

Thioesters are very important in biochemistry, mostly as a consequence of the fact that the molecule coenzyme A (CoA) has a free thiol group which reacts with carboxylic groups to form thioesters. The best known example is the molecule of acetyl-CoA.

It is thought that thioesters may have been precursors of life, as advocated by de Duve in "Thioester World":
It is revealing that thioesters are obligatory intermediates in several key processes in which ATP is either used or regenerated. Thioesters are involved in the synthesis of all esters, including those found in complex lipids. They also participate in the synthesis of a number of other cellular components, including peptides, fatty acids, sterols, terpenes, porphyrins, and others. In addition, thioesters are formed as key intermediates in several particularly ancient processes that result in the assembly of ATP. In both these instances, the thioester is closer than ATP to the process that uses or yields energy. In other words, thioesters could have actually played the role of ATP in a "thioester world" initially devoid of ATP. Eventually, [these] thioesters could have served to usher in ATP through its ability to support the formation of bonds between phosphate groups.

By the way, as a curiosity, if the oxygen from the ester group that is replaced by sulfur is the one of the double bond, the resulting functional group is called thionoester.

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Thiol group

The thiol group, or sulphydryl group or mercaptan group, is the functional group –SH. The prefix "thio" in this, and other functional groups, means that it has a sulfur atom instead of an oxygen (for example, there are also the thioester and thioether groups...). In this case, the ending suffix "ol", tells us that indeed this group is a group derived from an alcohol. That is, instead of the hydroxyl group –OH, we have sulfur in the place of the oxygen. One very important difference with respect to hydroxyl groups is related to the fact that the thiol groups present a weak acid behavior.
Since it has sulfur in its composition, the presence of thiol groups often confers to molecules an unpleasant odor.

Ether group

The ether functional group is characterized by the presence of an oxygen atom shared by two carbons (can be alkyl or aryl groups). It is therefore a functional group that appears in an internal position within the molecules. Its general formula is C1-O-C2.

 

The C-O-C bond angle has about 104.5 °, with a bonding distance of 140pm. The ether group is a polar functional group, because the COC bond angle is not 180°, which impairs the molecule dipoles to cancel each other. Although it cannot function as an H donor in hydrogen bonds, it can function as an acceptor of them.

In biochemistry, the ether groups are present, for example, in the O-glycosidic bonds.

Amide group

The amide group is originated when a carboxyl group reacts with an amine group. It is characterized by the presence of a carbon bounded to an oxygen through a double bond and to a nitrogen via a single bond.

Indeed, though this is the most common representation, the amide group displays an electronic delocalization involving the oxygen, carbon and nitrogen atoms. That is, the bound between carbon and oxygen is partially double, and the same is valid for the bound between the carbon and the nitrogen. This causes the amide group to present a rigid conformation, where these three atoms define a plane.

The amide group can be located at the end of a molecule, in which case the nitrogen is connected to two hydrogens, or may be in an internal position, causing the nitrogen to be connected to a hydrogen and a second carbon, or two different carbons.

Despite having a nitrogen atom, the amide group does not have a significant alkaline behavior.
In biochemistry the amide group appears in a prominent position because it is the functional group that exists in the peptide bonds.

The amide groups can be identified by infrared spectroscopy (it shows a VCO band at about 1650 cm-1).

Ester group

The ester group is characterized by being an internal functional group, that is, it does not appear in the ends of the molecules. It presents two oxygen atoms bound to the same carbon atom, one through a double bound and the other one through a single one (R1-COO-R2). It is a neutral polar group, that is, it does not possess acid or basic properties. It can establish hydrogen bounds, acting as a H acceptor.

It is formed by the reaction of a carboxyl and a hydroxyl functional groups. Putting it in a simple way, it is the result of the substitution of the hydrogen atom of a carboxyl group by an organic portion.

It can be identified by infrared sepctroscopy (it presents a band between 1730-1750 cm-1).

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Amino group

The amine group is characterized by the presence of a nitrogen atom with a pair of non-bonding electrons. It is derived from ammonia, where one or more hydrogens have been replaced by other atoms.

The amines can be divided into primary, secondary and tertiary. The primaries are those in which only one of three hydrogen atoms of ammonia was replaced by an alkyl chain. The secondary amines have two alkyl chains and the tertiary have three. The secondary and tertiary amines may be presented in a linear or cyclic form.

The amines may be designated in different ways. Typically, it is used the prefix amino-("aminoacid", for example) or the suffix-amine ("glucosamine," for example). When there is a substitution in the amino group, it is named starting with the prefix N-.
The amines can establish hydrogen bonds, since they have one H atom attached to a very electronegative atom (N in this case).
The amines act as weak bases, as they can capture a H+, due to the existence of a pair of non-bonding electrons in the nitrogen atom. They are the most relevant alkaline functional group in biochemistry.

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One more quiz about functional groups... :)

http://www.funtrivia.com/playquiz/quiz30262422a5408.html

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Carboxyl group

The carboxyl group is composed of two oxygen atoms bound to a carbon, one by a double bond and the other through a single bond. The latter is also covalently bonded to a hydrogen atom (R-COOH). Put simply, it can be seen as a functional group comprising a carbonyl group and a hydroxyl group.

The carboxyl group is the main acidic group in organic chemistry, and therefore can lose an H⁺, resulting in an anionic carboxylate group (R-COO^-). Carboxylate ions are stabilized by electronic resonance, which allows the carboxyl group to present a significant acidic behavior. Carboxyl groups are highly polar and can act as H donors and acceptors in hydrogen bonds.

In biochemistry, the carboxyl groups are sometimes removed from biomolecules in the so-called decarboxylation reactions (they are released in the form of CO₂).
The presence of carboxyl groups in the molecules can be detected by infrared spectroscopy, showing a characteristic vibration between 1680 and 1725 cm^-1. Alternatively, it can be identified by nuclear magnetic resonance, appearing in the region of 10-13 ppm.

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Another game about functional groups... :)

http://firstyear.chem.usyd.edu.au/games/flashcard.shtml?select=functional_groups

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Hydroxyl group

The hydroxyl group is a functional group characterized by the presence of an oxygen atom covalently bonded to a hydrogen atom (R-OH). It is also called alcohol group, and the molecules that contain it have in their names the suffix "ol". In biochemistry, this group is particularly important because it can act both as donor and acceptor of H in hydrogen bonds. Therefore, their presence in biomolecules increases their water solubility and hydrophilic character.

This is a non-charged polar group. However, in some biochemical contexts it can function as a weak acid, losing one H+. This behavior is particularly important in the case of phenolic hydroxyl groups, i.e., in the case of hydroxyl groups bounded to benzene rings. As the main example of this situation, we have the amino acid tyrosine, which in some proteins may have an acidic behaviour.

Game about functional groups

Here it is a link to a game about functional groups.

http://www.chemistry-drills.com/drill-1.php?q=gen

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Carbonyl group

The carbonyl group is characterized by the presence of an oxygen atom covalently linked via a double bond to a carbon atom. Depending on the position within the molecule to which it belongs, it can be called aldehyde group or ketone group. The first concerns the carbonyl groups that are located at an end of the molecule, that is, includes groups that are located on the first or the last carbon in the molecule. The ketone group refers to a carbonyl group which is at an internal position within the molecule. If the carbonyl is an aldehyde group, the molecule name ends with the suffix "al". If it is a ketone, it ends with "one".

Oxygen is more electronegative than carbon, which causes the carbonyl group to present a high polarity. As it is more electronegative, oxygen tends to relocate the electronic cloud, pulling it towards it. Consequently, carbon displays a partial positive charge and oxygen a partial negative charge.
Finally, it should also be noted that the term "carbonyl" can also be applied to carbon monoxide, when acting as a ligand in an inorganic or organometallic complex.
In the analysis of the composition of molecules, the carbonyl group can be identified by infrared spectroscopy (it absorbs between approximately 1600-1900 cm^-1) or nuclear magnetic resonance (about 160-220 ppm).

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