Hydrogen bonds in chemical problems, how to form hydrogen bonds

Hydrogen that is covalently bound to the electronegative atom x (fluorine, chlorine, oxygen, nitrogen, etc.) is close to the electronegative atom y (which is also the same as x), and hydrogen is used as a medium between x and y to generate x-h....Y-shaped keys. This bond is called a hydrogen bond. The binding energy of hydrogen bonds is 2-8 kilocalories (kcal).

Because of the combined action of many hydrogen bonds, it is very stable. In the case of the a-helix of the protein is n-h....Hydrogen bonds of type O, N-H in the case of double helix of DNA....o，n-h…n-type hydrogen bonds, because there are many hydrogen bonds in this way, so these structures are stable, in addition, water and other solvents are heterogeneous, also due to the formation of o-h between water molecules....O-type hydrogen bonding. Therefore, this is also the reason for the formation of hydrophobic bonds.

Methane, C, H have different electronegativity and different ability to attract electrons, so there is an offset in the electron pairs, which is a polar bond.

In general, similar solubility, i.e., polar soluble versus polar, non-polar versus non-polar soluble. But this is not absolute.

Upstairs correct. Hydrogen bonding can be referred to.

In addition to the situation mentioned on the first floor, hydrogen bonds also include unconventional hydrogen bonds, which can be combined in the form of hydrogen bonds by three or multiple ion centers, or they can form hydrogen bonds with conjugated electrons. Methane is a polar bond, and non-polar bonds only exist chemical bonds formed with the same atoms, and it is generally not possible to judge whether they are miscible or not according to the nature of covalent bonds.

Those who agree with the red and black plot, at the same time, add that methane, c, and h have different electronegativity and different ability to attract electrons, so the electron pairs are offset and are polar bonds, and methane is a positive four-sided spatial symmetrical structure, and the whole does not show polarity, and is a non-polar molecule.

Hydrogen Bond Formation Conditions:

1. A hydrogen atom that forms a strong polar bond with a very electronegative atom.

2. Hydrogen bond properties of b(f, o, n) part of the negative charge with small radius and large electronegativity, single electron pairs and single electron pairs: the electrostatic attraction between the hydrogen nucleus on the strong polar bond (a-h) and the large electronegativity, single electron pair and b atom of the particle.

In hydrogen bonds, x and y are the very electronegative f, n, and o atoms. However, C, S, CL, P and even Br and I atoms can also form hydrogen bonds under certain conditions, but the bond energy is usually low. Carbon also has the potential to produce hydrogen bonds when it is attached to several electronegative atoms.

For example, in chloroform CHCL3, the carbanine atom is directly connected to three chlorine atoms, and the electron cloud density around the chlorine atom is larger, so the carbon atom has a partial positive charge around it, and the carbon also participates in the formation of hydrogen bonds and plays the role of a proton donor. In addition, the carbon on the aromatic ring also has a relatively strong ability to withdraw electrons, thus forming ar-h....: weak hydrogen bond of type o (here ar denotes aromatic ring).

Aromatic rings, carbon-carbon triple bonds, or double bonds can all act as electron donors in some cases, forming hydrogen bonds with highly polar x-H (e.g., -O-H).

Hello, a substance, with or without hydrogen bonds, needs to meet the following conditions.

Contains atoms with great electronegativity such as N, O, and F;

n, o, f are connected to hydrogen;

It must be liquid or solid.

Although dimethyl ether has hydrogen and oxygen, hydrogen and oxygen are not directly connected, so hydrogen bonds cannot be formed.

The above conditions are at the secondary school level, in fact, hydrogen bonds can still be formed without meeting any of the above conditions, for example, chloroform is much more soluble than 1,1,1-trichloroethane in benzene, the reason is that the hydrogen of chloroform forms a hydrogen bond with the electron cloud of the large bond of the benzene ring (here also involves the induction effect, I will not go into details).

Hope it helps!

If you don't understand, please ask! Hope!

1. Hydrogen bonding is not a chemical bond, it is a type of intermolecular force.

If the hydrogen atom is close to the atom y y (0 f n, etc.) with large electronegativity and small radius, hydrogen is used as the medium between x and y to generate a special intermolecular or intramolecular interaction in the form of x-h·y, which is called hydrogen bonding.

2. Hydrogen bonds can usually be represented by x-hy. where x is attached to hydrogen by a covalent bond (or ionic bond), which has high electronegativity and can stabilize the negative charge, so hydrogen is easily dissociated and acidic (proton donor). Y, on the other hand, has a higher electron density and is generally an atom containing lone pairs of electrons, which easily attracts hydrogen protons and thus forms a three-center, four-electron bond with x and h atoms.

3. In typical hydrogen bonds, x and y are highly electronegative f, n, and o atoms. However, the C, S, C1, P and Br and I atoms can also form hydrogen bonds in some cases, but usually the bond energy is lower. Carbon also has the potential to produce hydrogen bonds when it is attached to several electronegative atoms.

For example, in chloroform CHC13, the carbon atom is directly connected to the three chlorine atoms, and the electron cloud around the chlorine atom is denser, so the carbon atom has a partial positive charge around it, and the carbon is also involved in the formation of hydrogen bonds, playing the role of a proton donor. In addition, the carbon on the aromatic ring also has a relatively strong ability to wither electrons, so it forms ar-h · · Weak hydrogen bond of type 0 (where ar stands for aromatic ring). Aromatic rings, carbon-carbon bonds, or double bonds can be used as electron donors to form hydrogen bonds with highly polar x-h (e.g., -0-h) under certain emotional conditions.

Hydrogen bonding is not a chemical bond and is an intermolecular force. Hydrogen is bound to the electronegative atom X by covalent bonds. If it is close to the atom y (ofn, etc.

The electronegativity is large, the radius is small, and x-h?s are produced between x and yA special intermolecular or intramolecular interaction in the form of y, known as hydrogen bonding.

Hydrogen bondingHydrogen bonding is an electrostatic action, which is another molecule other than van der Waals force. The size of the hydrogen bond is between the chemical bond and the van der Waals force, which does not belong to the chemical bond, but has bond length and bond energy, and the hydrogen bond has saturation and directionality.

Substances that can form hydrogen bonds between molecules generally have higher melting and boiling points for nucleoswimming, because when a solid is melted or a liquid is vaporized, in addition to destroying the van der Waals force, the intermolecular hydrogen bond must also be broken, thus requiring more energy to be consumed. Substances that can form intermolecular hydrogen bonds in similar compounds have a higher melting and boiling point than those that cannot form intermolecular hydrogen bonds.