Questions tagged [hydrogen-bond]

Bond between covalently bound hydrogen atom and atom possessing a lone pair of electrons.

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Hydrogen bonding of chlorine [duplicate]

Even though nitrogen is less electronegative than chlorine according to Pauling scale bit why don't it form hydrogen bonding as effective as of nitrogen ? ( Electronegativity valve of N =3.0,Cl=3.2)
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Why mixing water with ethanol produces heat energy? [closed]

Sorry if I'm asking something stupid but I'm trying to understand where this energy gets from. As far as I could find, it is not a reaction as both chemicals left unchanged, so it might have something ...
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Why does energy need to be “compensated” in order for solvation to occur?

I am currently learning about the physical properties of alcohols. I understand that the main intermolecular forces between alcohols and water are hydrogen bonds. When these two are mixed, the ...
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Boiling point of ethanamide vs propanamide

I just have a question regarding the boiling points of some primary amides. Ethanamide has a boiling point of 222 °C, while propanamide has a lower boiling point of 213 °C. Both amides are capable of ...
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Why dichlormethane is immiscible in water?

As we know like dissolves like. And DCM is a polar solvent and water is too a polar solvent. Also there ought to be a strong hydrogen bonding between the chlorine and hydrogen atoms. So why it's ...
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Diazo Coupling reaction with para substituted phenol?

Usually Diazo coupling occurs at para position until the para position is occupied , in which case coupling occurs at ortho position . While solving questions I found in both the cases as shown , ...
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Does increasing # of hydrogen bonds decrease the strength of these bonds?

I saw the question, "Is the strength of hydrogen bonding greater in hydrogen peroxide or water?" and it reminded me of a question I had about hydrogen bonding: If an oxygen on a water has a hydrogen ...
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Hydrogen Bonding in Water (MO theory)

Valence Bond Theory tells us that each of the “sp3” (in reality, 44% s character) oxygen line pairs in water can act as electron donors, but observing the MO diagram for water tells us that the 2 non-...
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Complementary base pairing

In the molecular structure of a DNA it is seen that purines (adenine and guanine) bind with pyrimidines (cytosine, uracil and thymine) through hydrogen bonds, and this is always between a purine and a ...
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Why are hydrogen-bonded compounds (such as NH3) excellent solvents for most lab reagents? [closed]

Hydrogen bonds are said to be one of the strongest molecular interactions in nature. Then why can most substances that interact through hydrogen bondig such as water and $\ce{NH3}$ able to dissolve a ...
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Can =NH2+ in Arginine's side chain form hydrogen bonding at physiological pH?

I know that at physiological pH, Arginine will have its $\ce{=NH}$ protonated to $\ce{=NH2+}$. I was wondering if this $\ce{=NH2+}$ can still form a hydrogen bond by being a donor? And does the ...
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Density change due to hydrogen bonding in water and other compounds [duplicate]

I know that the hydrogen bonding between the water molecules causes water to expand when frozen (compared to water at 4 degrees). Do other compounds that contains hydrogen such as hydrogen sulfide and ...
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What would be the intermolecular forces between the molecules of methanetetrol?

Methanetetrol has the following chemical formula: $\ce{CO4H4}$. It is also referred to as orthocarbonic acid. Since the molecule has a molecular geometry of a tetrahedron, similar to that of a ...
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How hydrogen molecule is formed? [closed]

How two hydrogen atoms come close to form a bond ? Textbooks refer to a potential energy diagram but what i cant understand is what is this potential energy if the atoms are neutral . How they come ...
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What is the best hydrogen bond acceptor in 2-amino-N-(3-hydroxyphenyl)acetamide?

I was preparing for my first exam in organic chemistry and came across this question. Draw a water molecule that is hydrogen bonded to the best anticipated hydrogen bond acceptor. 2-amino-N-(3-...
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Dimerisation of HOOC-COOH in non polar solvents

In a textbook I read, the following question is my doubt: Why is the answer B)? Why do the other molecules not dimerise? How does it work? (P.S- Why dosen't the B) option only form hydrogen bonds ...
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Stability of geometrical isomers in cycloalkanes

Among the following, which should be the most stable compound? 1)Cis-cyclohexane-1,2-diol 2)Trans-cyclohexane-1,2-diol 3)Cis-cyclohexane-1,3-diol 4)Trans-cyclohexane-1,3-diol My thought process is-...
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Hydrogen bonds - why not in HCl? [duplicate]

In a textbook1, I found the following clear definition of hydrogen bonds: The strongest secondary bonding type, the hydrogen bond, is a special case of polar molecule bonding. It occurs between ...
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Why is the intermolecular hydrogen bond between phenol and aniline stronger than the respective hydrogen bonds? [duplicate]

From NCERT class 12 part 1 The way I see hydrogen bonding is that it occurs due to intermolecular charge interaction. The more electronegative nitrogen/oxygen due to the inductive effect the ...
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1answer
339 views

Why is the melting point of hydrogen fluoride lower than that of ammonia?

The melting point of hydrogen fluoride is -83.6°C, as compared to that of ammonia, which is -77.73°C. How does this make any sense? Both hydrogen fluoride and ammonia show hydrogen bonding, which "...
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1answer
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Non-conventional polymers

IUPAC defines a monomer as, A molecule which can undergo polymerisation thereby contributing constitutional units to the essential structure of a macromolecule. Bearing this in mind, I thought ...
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Explain the effect of intramolecular hydrogen bonding on solubilities in cold and hot water?

There is a statement given in my textbook (Cengage, Organic Chemistry (Part 1), page 4.33) which is as follows: (I edited the statement to make it simpler) One can account for the solubilities of ...
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What is Hydrogen bond Auto-correlation function

Can somebody explain the Hydrogen bond Auto-correlation function in Computational Chemistry (Molecular Dynamics and Simulations) and what does Intermittent and Continuous Hydrogen bond means? Why ...
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Hydrogen bonding in chloral hydrate

Normally, chlorine doesn't form hydrogen bonds because despite its electronegativity, the size of the atom is such that its electron density is too low to form hydrogen bonds. However, chlorine forms ...
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1answer
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Why are highly branched alcohols solid?

Usually branching (or decrease in surface area) leads to increased volatility. But in case of alcohols, my book states that: The higher alcohols (butanols to decanols) are somewhat viscous, and ...
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Which has stronger hydrogen bonds: water or ice?

As ice is the solid form of water and it has more hydrogen bonds than water, because it's oxygen atoms are precisely tetrahedrally positioned and each oxygen is hydrogen bonded by four neighbouring ...
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Why only F, O and N form Hydrogen Bonds? [duplicate]

Why only fluorine, oxygen and nitrogen can form hydrogen-bonds with the hydrogen of another molecule?
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Hydrogen bond strength of trichloromethane and chloromethane

Chloromethane has a larger dipole moment than trichloromethane. Does that mean that the hydrogen bond (C-H...O type) between chloromethane and acetone is stronger than that of trichloromethane and ...
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electronegativity and hydrogen bonding [duplicate]

I have a basic idea why, but can someone just confirm, why chlorine isn't able to hydrogen bond despite the fact that it has the same electronegativity value as nitrogen.
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How to characterise lipophilicity?

I was provided with a drug compound which is filling a hydrophobic pocket. The R group is changed and effects on the potency was measured; $\ce{R = -H, -CH3, -CH2F}$ were tested. As expected, the more ...
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How to determine the pH range at which maximum hydrate is present?

Question: Find the $\mathrm{pH}$ range at which maximum hydrate is present in a solution of oxaloacetic acid (given $\mathrm{pK_a}$ of $\ce{-COOH}$ in the left is $=2.2$ and on the right is $=3.98$)...
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Strongest hydrogen bond between neutral molecules?

It is known that very strong hydrogen bonds can occur in charged systems, such as $\ce{[F-}\ce{-H+-F-]}$, while hydrogen bonds in neutral systems are much weaker in comparison. What is the strongest ...
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How to identify hydrogen bonds and other non-covalent interactions from structure considerations?

Chemistry is governed by a wide range of interactions, from ionic and covalent bonding, or other types of strong interactions, towards weaker types of bonding, attraction, or repulsion, that typically ...
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Will the carboxylate groups of the citrate anion undergo hydrogen bonding?

The citrate anion of trisodium citrate has three carboxylate groups. I am concerned with whether or not there will be hydrogen bonding in water, with hydroxyl groups of other ions or alcohols. It has ...
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Does deuterium exhibit hydrogen bonding?

I searched for this on Google but I only got research articles in the SERP. I know of the concept of hydrogen bonds, that they are a special class of van der Waals forces between highly ...
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1answer
777 views

Why is the boiling point of hydrogen sulfide higher than that of hydrogen chloride?

The boiling point of $\ce{H_2S}$ is higher than $\ce{HCl}$. Is this due to the greater number of hydrogen bond that $\ce{H_2S}$ can form compared to $\ce{HCl}$? I found this explanation for the ...
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H-bonding in methanol and methoxyamine [duplicate]

The question was to determine if the substances made H-bonding between themselves and to represent it. In the following photos i'm showing my doubt about the H-bond in $\ce{CH3OH}$. In the solution (...
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4answers
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Why H2O is a liquid (water) and H2S is a gas?

I always think about this question. Is it due to attraction or repulsion or is there something else that makes one of them a gas and the other a liquid (water)?
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Boiling points of HF, HCl, HI [closed]

I'm really confused over how to weigh the molecular mass with intermolecular forces such as hydrogen bonding in HF in terms of figuring out the melting points in relation to each other. I know that ...
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2answers
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Is it possible for Cytosine and Hypoxantine to make three hydrogen bonds?

I think the O from Hypoxanthine can bond with one of the Hs in NH2 from Cytosine and the H that is connected to N in Hypoxanthine with the N in Cytosine but is it possible also for the H connected to ...
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Is the surface of glass a fine layer of silanol?

Today we learned in class through a vivid demonstration that water sticks to glass. We were then taught that water sticks to glass because while glass is mainly composed of silicon dioxide, the ...
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Is the strength of hydrogen bonding greater in hydrogen peroxide or water?

When we compare water and hydrogen peroxide's hydrogen bond strength, which one should have the greater one? I know that peroxide has more hydrogen bonds, but when we compare the strength of each ...
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Why is chitin ordinarily insoluble in water, but soluble after deacetylation? [closed]

Chitin is usually insoluble in water. How does its chemical structure explain this? Furthermore, when chitin undergoes deacetylation, it becomes soluble and forms hydrogen bonds with water. How is ...
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Why is density of water maximum at 4 degree celsius?

Why is density of water maximum at 4 degree celsius? We were having a discussion to this question in class and I could gather the following points. 1) $H_2O$ exists in a cage like structure in ice ...
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Solubility of CHCl3 in water

Why isn't $\ce{CHCl3}$ soluble in water? Why doesn't $\ce{CHCl3}$ participate in hydrogen bonding in water like $\ce{CH3CN}$ as $\ce{Cl}$ can make the $\ce{C-H}$ bond polar like $\ce{CN}$ does?
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Is a temperature decrease required for hydrogen bonds to form in water?

As I understand it, increasing the temperature of water causes hydrogen bonds to break. Does this mean that a decrease in temperature is required for the formation of those hydrogen bonds?
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Relationship between freezing point depression and hydrogen bonds

Freezing point of a solvent is decreased due to the added solute particles in it. e.g. ions. Therefore electrolytes contribute to lowering freezing point (say for physiological conditions). If a ...
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Which oxygen will form a better hydrogen bond?

Which oxygen will form a stronger hydrogen bond , the one in water or the one in hydrogen peroxide ?? According to me , the one in peroxide will form the stronger H bond as the O here being less ...
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How does hydrogen bonding affect the boiling points of chemical compounds?

My main question is why is the boiling point of methanol so much different from that of water? I understand that both compound are able to develop hydrogen bonding, and obviously water can develop ...
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What is a hydrogen bond acceptor and donor?

I recently read about hydrogen bonding. One thing about which I am really confused is how to distinguish between hydrogen bond acceptors and donors. I looked it up on SE and found this post, which ...