Questions tagged [hydrogen-bond]

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

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Comparison of boiling points via hydrogen Bonding [on hold]

1)Boiling point of ethanol is more than that of ethanamine but boiling point of ethanoic acid is less than that of ethanamide...why is this so? I understand that the approach would be to check the ...
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Why does ammonia have higher melting point but lower boiling point than HF? [duplicate]

I guess the reason is hydrogen bonding, but shouldn't both the trends be similar in that case?
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Steric inhibition of resonance vs. hydrogen bonding

I have to compare the acidic strength of these compounds: Now, in A and B hydrogen bonding will be present which will help stabilize the negative charge of the conjugate base. However, the hydroxyl ...
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Does alcohol hydrogen in the enol tautomer of a β-dicarbonyl have sp² character?

My reasoning for the somewhat implausible "$\mathrm{sp^2}$" character of the hydrogen between these two oxygens on the enol structure of the right comes from recognizing that if it were, then we would ...
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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 HCl not considered to have hydrogen bonding?

A molecule that has hydrogen bonding usually follows these two premises. 1.) There is a hydrogen atom involved 2.) Hydrogen must be bonded to a highly electronegative element which are ...
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Do symmetric hydrogen bonds in neutral molecules exist?

As far as I know, there have only few truly symmetric hydrogen bonds been observed. Unquestionable is the existence of it in the bifluoride ion, $\ce{[F-H-F]-}$, see also here. There are a couple of ...
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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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How does intramolecular hydrogen bonding cause the molecules to be separated from each other?

I learnt about intramolecular hydrogen bonding today, which occurs between molecules such as ortho-nitrophenol. What I was told is that in case of intramolecular bonding, the molecules separate from ...
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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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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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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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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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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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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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Effect of temperature on Hydrogen Bonding?

We had this question in a test and I am not sure of the answer Q. Temperature changes don't effect the extent of inter and intra molecular hydrogen bonding. State true or false. I think that ...
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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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Hydrogen bonding relating to molecular orbital theory

In [1, p. 232] here is an explanation of how alcohols hydrogen bond to each other and I do understand how the alcohols form hydrogen bonds to each other: FIGURE 6.15 Water and alcohols are ...
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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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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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How can the hydrogen bonds in solid HF be best represented?

The hydrogen bonds in solid HF can be best represented as: The correct answer is supposed to be (c), but I don't understand why this is so. Does the strength of hydrogen bonding depend on the $\...
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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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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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Why is the boiling point of stibane higher than that of ammonia?

I recently came across the fact that the boiling point of $\ce{SbH3}$ (stibane) is greater than that of $\ce{NH3}$ (ammonia). I was expecting $\ce{NH3}$ to have a greater boiling point as a ...
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Hydrogen bonding in solid bicarbonates

Why is there two different kinds of hydrogen bonding in solid bicarbonates $\ce{NaHCO3}$ and $\ce{KHCO3}$? In both cases we consider anions of each for hydrogen bonding . The anions involved in ...
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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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Why is ice less dense than water?

I know the traditional explanation, which says that ice has large spaces between $\ce{H2O}$ molecules because hydrogen-bonding gives it an open structure. But what does the open structure have to do ...
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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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Relative strengths of hydrogen bonds

Order of hydrogen bond strength: $\ce{O-H...N}$ > $\ce{O-H...O}$ > $\ce{N-H...N}$ > $\ce{N-H...O}$. Why is that so? According to me $\ce{O-H...O}$ should have the maximum strength while $\...
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Can 1 gram hyaluronic acid really hold 6L of water?

According to this study (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3970829/), they make an (uncited) claim about hyaluronic acid: "One of its most important properties is that it can attach and ...
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If hydrogen bonding in water was weaker, what happens to H+ ion concentration?

Water ionization becomes much less evident if the hydrogen bonds are just a few percent stronger but pure water contains considerably more $\ce{H+}$ ions if they are few percent weaker. I found this ...
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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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How to determine what organic molecule has the highest boiling point?

Compare and answer which one has the highest boiling point: $\ce{CH3CH2CH2CH3}$ (butane) ... [$\pu{−1}$ to $\pu{1^\circ C};\ 30$ to $\pu{34^\circ F};\ 272$ to $274\ \pu K$] $\ce{CH3NH2}$ (...
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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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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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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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Polymer Crystallinity

See the following question: I think the answer is A because of the hydrogen bond in the side group, thus the degree of secondary bonding between parallel chain segments is higher. Is my thinking ...
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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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How to determine what compounds form hydrogen bonds? [closed]

Which of the following compounds can form hydrogen bonds? a. $\ce{H2S}$ b. $\ce{CH3OCH3}$ c. $\ce{HCl}$ d. $\ce{BH3}$ e. $\ce{NH3}$ Why isn't $\ce{CH3OCH3}$ since $\ce{H}$ is bonded with $\ce{O}$ ...
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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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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 ...