In a hydrogen bond, the lone pair electrons on oxygen, nitrogen, or fluorine interact with the partial positive hydrogen that is covalently bonded to one of those atoms. The hydrogen atom in a hydrogen bond is shared by two electronegative atoms such as oxygen or nitrogen. Hydrogen bonds are responsible for specific base-pair formation in the DNA double helix and a major factor to the stability of the DNA double helix structure. A hydrogen-bond donor includes the hydrogen atom and the atom to which it is most tightly linked with.
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The hydrogen-bond also play a very important roles in proteins' structure because it stabalizes the secondary, tertiary and quaternary structure of proteins which formed by alpha helix, beta sheets, turns and loops. The hydrogen-bond connected the amino acides between different polypeptide chains in proteins structure. The hydrogen-bond acceptor is the atom that is less tightly linked to the hydrogen atom. Hydrogen bonds are fundamentally electrostatic interactions and are much weaker than covalent bonds. They are, however, the strongest kind of dipole-dipole interaction.
The electronegative atom to which the hydrogen atom is bonded with pulls electron density away from the hydrogen atom, developing a partial positive charge. Therefore, the hydrogen atom can then interact with a partial negatively charged atom through an electrostatic interaction. Hydrogen bonding is a form of electrostatic interaction between a hydrogen atom bonded to two electronegative atoms; one of which is the hydrogen-bond donor that has a stronger bond between itself and the hydrogen.
These electronegative atoms are nitrogen, oxygen, and fluorine; this electronegative atom pulls electron density away from the hydrogen atom, giving it a partially positive charge. This partial positive charge is attracted to the partial negative charge of the hydrogen bond acceptor an electron density rich atom. The chemical bond formed between the hydrogen-bond donor, hydrogen atom, and hydrogen-bond acceptor has a straight, linear structure. Hydrogen bonding H-bond is a non-covalent type of bonding between molecules or within them, intermolecularly or intramolecularly.
This type of bonding is much weaker and much longer than the covalent bond and ionic bonds, but it is stronger than a van der waals interaction. It also carries some features of covalent bonding: direct and straight. In other words, H-bond donor and H-bond acceptor lie along the straight line.
In order to form an H-bond, an H-bond donor and H-bond acceptor are required. The H-bond donor is the molecule that has a hydrogen atom bonded to a highly electronegative, small atom with available valence N, F, and O follow the above description the best because they are very electronegative, making H, which is covalently attached to them, very positive.
The H-O, H-N, and H-F bonds are extremely polar; as a result, the electron density is easily withdrawn from the hydrogen atom towards the electronegative atom. The partially positive hydrogen in one molecule attracts to partially negative lone pair of the electronegative atom on the other molecule and H-bond forms as a result of such an interaction. All the hydrogen bonds vary in strength. Other important facts about hydrogen bonding are as follows. The small sizes of nitrogen, oxygen, and fluorine are essential to H bonding for two reasons.
One is that it makes those atoms electronegative that their covalently bonded H is highly positive. Other reason is that it allows the lone pair on the other oxygen, nitrogen, or fluorine to come close to the H. Also, hydrogen bonding has a profound impact in many systems.
Hydrogen bonding is also involves in the action of many enzymes [The Molecular Nature of Matter and Change]. Ammonia, water, and hydrogen fluoride all have higher boiling points than other similar molecules, which is due to hydrogen bonds. Bonds between hydrogen and these strongly electronegative atoms are very polar, with a partial positive charge on hydrogen.
This partially positive hydrogen is strongly attracted to the partially negative oxygen on the adjacent molecule. In general, boiling points rise with the increase molecular weight, both because the additional mass requires higher temperature for rapid movement of the molecules and because heavier molecules have a greater London forces. Water's freezing point is also much higher than other similar molecules. An unusual feature is that it decreases in density when it freezes. The tetrahedral structure around each oxygen atom, with two regular bonds to hydrogen and two to other molecules.
This requires a great amount of space between the ice molecules. Clathrates are molecules trapped in holes of solid, like ice, that is theorized to be able to be used as anesthesia.
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Hydrogen bonding has a significant influence on a molecule's boiling points. The boiling point usually increases with the increase of the molar mass. However, molecules that are involved in intermolecular H-bonding bonding have much higher boiling points in comparison with the molecules of the same molar mass that are not involved in H-bonding.objectifcoaching.com/components/comal/rencontre-trans-aix-en.php
Uses of Fluorine in Chemotherapy | SpringerLink
This is because the unusually strong H-bonding forces allow for stronger interaction between water molecules and therefore creating a stronger bond and higher boiling point. Hydrogen bonding can occur between hydrogen and four other elements. Oxygen most common , Fluorine, Nitrogen and Carbon. Carbon is the special case in that it only really interacts in hydrogen bonding when it is bound to very electronegative elements such as Fluorine and Chlorine. Hydrogen bonding is an important component of the three major macromolecules in biochemistry such as proteins , nucleic acids , and carbohydrates.
The H-bonding is responsible for the structure and properties of proteins enzymes. Hydrogen bonding is applicable in these biomolecules because of functional groups present. Some such are the carboxylic acid, alcohol or even amine groups. These provide either an hydrogen, oxygen or nitrogen for possible hydrogen bonds. As previously mentioned, hydrogen bond can be intermolecular ex.
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Fluorinated carbohydrates : chemical and biochemical aspects
This property, whereby desolvation of fluorinated surfaces and weak dipolar interactions in organized media drive molecular recognition see schematic representation , is argued to be a useful design principle and a likely explanation for the abundance of fluorinated compounds in medicinal chemistry. Volume 5 , Issue 5. The full text of this article hosted at iucr. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account.
Fluorinated Carbohydrates: Chemical and Biochemical Aspects (ACS Symposium Series)
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