Questions tagged [halides]

Chemical compounds that contain halogens (group 17 in the Periodic Table) as part of their chemical structure. This tag should only be applied where the halide group is one of the main focuses of the question.

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56
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1answer
7k views

Why does F replace the axial bond in PCl5?

Why does $\ce{F}$ replace an axial bond in $\ce{PCl5}$? I realize that it would be more stable there than at equatorial bond, but what is the reason of its stability? Similarly in $\ce{AB4}$ type of ...
46
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8answers
30k views

Why do compounds like SF6 and SF4 exist but SH6 and SH4 don't?

Both $\ce{SF6}$ and $\ce{SH6}$ and $\ce{SF4}$ and $\ce{SH4}$ have the same central atom and the same hybridization, but my teacher specifically mentioned that $\ce{SH6}$ and $\ce{SH4}$ don't exist. I'...
34
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2answers
12k views

Why does cyclopropane react with bromine?

In my exam, I was asked why cyclopropane could decolourise bromine water (indicating that it reacted with the bromine). All I could guess was that it is related to the high angle strain in ...
17
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2answers
6k views

Is HF the least acidic hydrogen halide?

Fluorine is the most electronegative halogen and therefore, there is larger difference in electronegativity between the atoms of $\ce{HF}$ than any other hydrogen halide, which means the positive ...
31
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5answers
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Why does alcoholic KOH prefer elimination whereas aqueous KOH prefers substitution?

What is the basic difference between aqueous and alcoholic $\ce{KOH}$? Why does alcoholic $\ce{KOH}$ prefer elimination whereas aqueous $\ce{KOH}$ prefers substitution?
19
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3answers
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Explanation for the trends in nucleophilicity—Orbital interactions or electrostatic attraction

The trend of halide nucleophilicity in polar protic solvents is $$\ce{I- > Br- > Cl- > F-}$$ The reasons given by Solomons and Fryhle[1], and by Wade[2] are basically as follows. Smaller ...
9
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1answer
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Hydrogen halide acidity

Why is it that $pK_{\ce{a-HF}} \lt pK_{\ce{a-HCl}}\lt pK_{\ce{a-HBr}}\lt pK_{\ce{a-HI}}$, although the electronegativity decreases? The more electronegative the atom accompanying hydrogen, the lower ...
6
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1answer
4k views

What is the hybridization of chlorine in vinyl chloride?

Is chlorine in vinyl chloride sp2 or sp3 hybridized? Calculating using steric number it is found to be sp3 hybridized. But according to I. L. Finar* it is sp2. *I.L. Finar: Organic chemistry Vol.1 ...
3
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2answers
14k views

What is hybridisation of XeF6 in solid state?

According to the following formula: Type of hybridisation/steric no. = (no. of sigma bonds + no. of lone pairs) it should be $\ce{sp^3d^3}$, however according to my textbook it is $\ce{sp^3d^2}$ in ...
5
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1answer
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Why do sodium halides react so differently with sulfuric acid?

Why do sodium halides react so differently with sulfuric acid? \begin{align} \ce{NaF + H2SO4 &-> NaHSO4 + HF} \tag{1a}\label{NaF}\\ \ce{NaCl + H2SO4 &-> NaHSO4 + HCl} \tag{...
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1answer
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What is the molecular structure of xenon hexafluoride?

Xenon hexafluoride, $\ce{XeF6}$, can be obtained by reaction of xenon with excess fluorine gas. What is the gas-phase structure of the molecule? What experimental evidence is there to support it, ...
17
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2answers
1k views

Why is WF6 stable whereas CrF6 is unknown?

$\ce{F-}$ is a hard base since it is small and relatively polarizable. Both $\ce{Cr^6+}$ and $\ce{W^6+}$ are hard acids, but shouldn't $\ce{CrF6}$ be favored since it would be a smaller hard acid?
15
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1answer
764 views

Alphabetization rule in case of consecutively placed substituents

This is the compound: I am stuck on assigning the locants to the given halo substituents. We know that all halogens are of equal priority. So, using first point of difference, we get either an $\ce{I ...
4
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2answers
13k views

Structure of xenon hexafluoride

The central atom has a hybridization of $\mathrm{sp^3d^3}$. Thus, its structure should be pentagonal bipyramidal. Why is it not that but a distorted octahedron?
5
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1answer
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Is an SN1 reaction possible in halobenzene?

Is an SN1 reaction possible in halobenzene? Will the phenyl carbocation be stabilized via resonance? Suppose the leaving group is very electronegative and the environment is protic. What then would ...
7
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3answers
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Why does chloromethane have a larger dipole moment than chloroform?

Why does $\ce{CH3Cl}$, methyl chloride, have a larger dipole moment than $\ce{CHCl3}$, chloroform? Let us consider $\ce{C-Cl}$ bond moment to be $x$ and that of $\ce{C-H}$ bond to be $y$. In $\...
10
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2answers
684 views

What is the structural formula of alkali hypohalite: MOX or MXO?

There seems to be an inconsistency in the formula. Somewhere it is written as MOX and in some places, it is written as MXO. This is what Google gives when you search sodium hypochlorite: I think the ...
16
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5answers
8k views

Can fluorine act as the central atom in interhalogen compounds?

Why can't fluorine be the central atom in inter-halogen compounds? A $\ce{F-F}$ bond is weaker than a $\ce{F-X}$ bond and thus, fluorine should be happy to form inter-halogen compounds. But, why ...
6
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3answers
2k views

Relative acidity of p-chlorobenzoic acid and p-flurobenzoic acid

I want to compare the relative acidity of p-chlorobenzoic acid and p-flurobenzoic acid. Both of the facts below point to p-chlorobenzoic acid being more acidic: The carboxylic acid group is too far ...
15
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1answer
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Why do halogen-metal exchanges happen?

I'm trying to understand organometallic raegents but am stuck at halogen-metal exchanges. For example if you have $\ce{PhBr + BuLi}$ you get $\ce{PhLi + BuBr}$, I don't understand why $\ce{PhBu + ...
13
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1answer
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Why does treatment of a geminal dihalide with sodium amide lead to an alkyne and not an allene?

I've come across the following problem in Klein's Organic Chemistry, 2nd edition: However, I'm a little bit confused about why the terminal alkyne is produced. I believe that an allene should be ...
6
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1answer
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Trend in the boiling point of the hydrogen halides

The boiling points of the hydrogen halides are as follows: $$\begin{array}{cc} \hline \text{Species} & \text{Boiling point / }\mathrm{^\circ C} \\ \hline \ce{HCl} & -85.1 \\ \ce{HBr} & -...
7
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1answer
435 views

What does the molecular orbital scheme of beryllium chloride and hydride look like?

Beryllium is a somewhat fascinating element since it is the only member of the second group that behaves somewhat non-metalish and, e.g. forms a somewhat covalent chloride and a covalent hydride. In ...
5
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2answers
527 views

Is the 5d orbital involved in triiodide ion?

Is the $5\mathrm{d}$ orbital involved in the triiodide ion, $\ce{I3-}$? There are $5$ electron pairs around the central iodine. (Almost) all of the hypervalent compounds involve the most ...
4
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2answers
4k views

Reaction of ethylene glycol with PI₃ (P + I₂)

We know that $\ce{2P + 3I2 -> 2PI3}$ Ethylene glycol reacts with $\ce{PCl3}$ to give ethylene dichloride, but why does it gives ethylene when it reacts with $\ce{P + I2}$? I don't really know ...
3
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1answer
1k views

Order of citation of alkyl and halide prefixes in IUPAC names

I've been playing around with ChemDraw and found that it assigns the priorities of substituents in a way I wouldn't have expected, depending on the length of the alkyl substituent. I'm not a ...
3
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2answers
3k views

Should carbon tetrachloride really be considered an organic compound?

Wikipedia says: Carbon tetrachloride […] is an organic compound with the chemical formula $\ce{CCl4}$. From an organic point of view, carbon tetrachloride can be called the tetrachloro ...
16
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2answers
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Why is sulfur hexafluoride more stable than selenium or tellurium hexafluoride?

I was just reading about p Block elements from two different books. Both books say that $\ce{SF6}$ is extremely stable in 16th group due to steric reasons but my question is why is it more stable than ...
20
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3answers
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Please explain why dioxygen difluoride is so dangerous

I just read this article that mentioned that dioxygen difluoride is very dangerous. The terms it uses are "awful", "violently hideous" and "deeply alarming". But I couldn't get a handle on exactly ...
22
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2answers
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Why do XeO and XeF8 not exist?

Since Neil Bartlett's 1962 discovery that xenon was capable of forming chemical compounds, a large number of xenon compounds have been discovered and described. Almost all known xenon compounds ...
8
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3answers
555 views

Substitution at thionyl chloride sulfur

What is the correct way of writing the mechanism for substitution at the sulfur atom of thionyl chloride: Should one write the cleavage of the $\ce{S-O}$ π bond? The argument for the first ...
7
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0answers
294 views

Why do chlorinated silanes have lower boiling points than their methane analogs?

The boiling points of the chlorinated silanes and methanes are given below: $$\begin{array}{ccc} \hline \text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
6
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1answer
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Reaction of an alkyl halide with silver nitrite

I want to know that whether both alkyl nitrite and nito alkane are produced or if nitroalkane is the only product. There are many different (contradicting) things written in different books that is ...
5
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1answer
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Why is fluorine more reactive than iodine despite the weaker I-I bond?

The atomic radius of halogens increases as we go down the group due to the addition of new shells. As a result, the bond length of halogen $\ce{X-X}$ increases down the group. So, less energy is ...
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2answers
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Why is caesium considered the most reactive element and not fluorine? [closed]

Some people say caesium is most reactive element. I thought it to be fluorine as it is the element that reacts with almost all elements (except couple of inert gases). But caesium won't react many of ...
7
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1answer
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Hydrolysis products of chlorides of group 15

$\ce{NCl3}$ on hydrolysis produces $\ce{NH4OH}$ and $\ce{HOCl}$. $\ce{PCl_3}$ when hydrolyzed produces $\ce{P(OH)3}$ i.e. $\ce{H3PO3}$. $\ce{AsCl_3}$ when hydrolyzed produces $\ce{As(OH)3}$. ...
7
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2answers
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How exactly does the reaction between alkyl halides and silver nitrite occur?

$$\ce{R-X + AgNO_2 -> RNO_2}$$ Now depending on the $\ce{R}$ and solvent the reaction can occur via $\mathrm{S_N1}$ or $\mathrm{S_N2}$. When the reaction proceeds via $\mathrm{S_N1}$ the product ...
6
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1answer
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Can the hydroxyl group of 4-hydroxybenzoic acid react with phosphorus pentachloride?

I learned that, a phenol will not react (or react very slowly) with $\ce{PCl5}$ due to its stabilized structure. How about the $\ce{-OH}$ group on the benzene ring of 4-hydroxybenzoic acid? Will that ...
5
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1answer
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Why is it possible to form bromoalkanes but not iodoalkanes from free radical substitution?

For a free radical substitution (FRS) reaction between iodine $\ce{I2}$ with ethane and bromine $\ce{Br2}$ with ethane $\ce{CH3CH3}$: $E_\mathrm d(\ce{H-I})=299\ \mathrm{kJ\ mol^{-1}}$ $E_\mathrm d(\...
5
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2answers
829 views

Does the compound KFO₃ exist?

As the compound potassium chlorate exists, is there something as $\ce{KFO3}$? All the other halogenates are mentioned somewhere on the web but what about this? If no, then why?
4
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1answer
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Why do the boiling and melting points decrease as you go down group 1 and vice versa for group 7?

I used to think that because an alkali metal needs to lose one electron to complete its outer shell, when the atom increases in size (atomic radius), the electron would be easier to lose as the ...
6
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1answer
943 views

Elimination of HCl from isomeric chlorocyclohexadienes

Which of these is most easily dehydrohalogenated? a. 5-Chlorocyclohexa-1,3-diene (1) b. 3-Chlorocyclohexa-1,4-diene (2) c. 1-Chlorocyclohexa-1,4-diene (3) d. Both 1 and 3 I encountered this question ...
13
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1answer
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Why is the dipole moment of chloromethane larger than the dipole moment of fluoromethane?

On the Pauling electronegativity scale, fluorine and chlorine are 3.98 and 3.16, respectively. Since the dipole moment is dependent on electronegativity, why is the dipole moment of chloromethane ...
10
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1answer
5k views

Why does water favour nucleophilic substitution over elimination?

The two broad ways a halogen can leave a haloalkane are nucleophilic substitution and elimination reactions. I was told that elimination reactions (that form a double bond as a $H^+$ is also removed) ...
11
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1answer
989 views

Order of halide nucleophilicity in DMF

The order of nucleophilicity for halide family in DMF is: $\ce{Cl- > Br- > I-}$. I understand the reason for this must be that DMF, being a polar aprotic solvent, is unable to solvate the ...
7
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1answer
9k views

Enthalpies of formation of alkali metal halides

Shriver and Atkins's Inorganic Chemistry has this graph: How can I explain the different direction of the trends for fluorides and chlorides? I know that the decreasing lattice energy (as M goes from ...
7
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2answers
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Bromination of acetanilide

Why does acetanilide gives exclusively para isomer. I know that -I of nitrogen must decrease the yield of ortho product, but still it should be made in accountable amounts. Where am I going wrong. I ...
6
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7answers
23k views

The solubility of haloalkanes in water

Haloalkanes aren't very soluble in water because they can't form hydrogen bonds, and the energy required to break hydrogen bonds in water etc is higher than the energy released when new bonds between ...
5
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0answers
954 views

Why PI3 is not used in HVZ reaction?

With the help of HVZ reaction, we can get alpha-chloro or alpha-bromo carboxylic acid. But can we make alpha-iodocarboxylic acid with the help of HVZ reaction? I could not find any reference of HVZ ...
4
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1answer
335 views

Stability of 3d metal fluorides and iodides in different oxidation states

I read that the fluorides of 3d metals in lower oxidation states, e.g. $\ce{VF2}$, $\ce{TiF2}$, and $\ce{CuF}$ are thermodynamically unstable. For example, $\ce{CuF}$ disproportionates to $\ce{Cu + ...