The Stack Overflow podcast is back! Listen to an interview with our new CEO.

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.

Filter by
Sorted by
Tagged with
52
votes
1answer
6k 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 ...
51
votes
2answers
4k views

How does chloroform degrade nitrile gloves?

Many of us have experienced the failure of nitrile gloves when exposed to chloroform. What's going on at a mechanistic level when this occurs? I would guess that the chloroform dissolves some of the ...
44
votes
8answers
27k 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'...
31
votes
2answers
8k 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 ...
28
votes
1answer
2k views

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, ...
27
votes
1answer
4k views

Why is fluorine a gas, but lithium isn't?

$\ce{F2}$ is a gas, but pure lithium is a solid metal. Why is this? Lithium is much lighter, just 3 protons and 3.9 neutrons (average). Fluorine is much heaver, 9 protons and 10 neutrons.
27
votes
4answers
30k views

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?
21
votes
2answers
3k views

Storing hydrofluoric acid before the invention of plastics

The first person to synthesize hydrofluoric acid in large quantities was Carl Wilhelm Scheele in 1771. This acid is known for its ability to corrode glass and metals. What materials were the ...
21
votes
2answers
6k views

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 ...
20
votes
3answers
11k views

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 ...
20
votes
3answers
343 views

Why don't alkynes undergo preferential anti bromination to the degree that alkenes do?

Alkenes, for the most part (unless there is a phenyl group or highly ionising solvent) undergo almost exclusively anti addition of bromine. However, under similar conditions alkynes, although undergo ...
19
votes
2answers
245 views

What happens chemically to 5'-radiolabeled aqueous thyroxine (thyroid prohormone) when its I-131 undergoes beta+gamma decay?

Related to this question about $\ce{^{14}C}$ beta decay in $\ce{CO2}$, what happens when the $\ce{^{131}I}$ in radiolabeled thyroxine (thyroid prohormone, or "T$_4$") undergoes beta-plus-gamma decay ...
18
votes
1answer
7k views

Why are the halogens good disinfectants?

I've been searching around the internet for a while and I know that Chlorine, Bromine and Iodine are used as disinfectants. My question is, what is the property of the halogens that make them ...
16
votes
2answers
4k views

Why 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 ...
16
votes
2answers
796 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?
16
votes
2answers
1k views

Gauche effect and bond length

Which of the following compounds has the longest bond length? (A) $\ce{H3C-CF3}$ (B) $\ce{FCH2-CH2F}$ (C) $\ce{F2CH-CHF2}$ (D) $\ce{F3C-CF3}$ My logic was based on the relative ...
15
votes
2answers
3k views

Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene?

Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene? Usually, trans compunds are more stable than cis ones, due to less strain and its non-polarity. But, in this case it's quite ...
15
votes
5answers
7k 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 ...
15
votes
1answer
603 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 ...
15
votes
1answer
3k views

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 + ...
15
votes
1answer
1k views

Why does 2-chloropropane's mass spectrum have a peak at 27?

I have noticed that all halogenoalkanes of the form 2-Xpropane seem to have a mass spec peak at 27, implying that a $\ce{C2H3+}$ ion is being formed. Forming a $\ce{C2H3+}$ ion, however, would mean ...
14
votes
2answers
7k views

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 ...
14
votes
2answers
2k views

Why does fluorine act as a leaving group in organophosphates?

C-F bond is the strongest single bond in organic chemistry with a bond energy of $\ce{453 kJ\,mol^{-1}}$. And it is very difficult to break this bond and F does not act as a leaving group. However, ...
14
votes
3answers
3k views

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 ...
13
votes
2answers
1k views

Is there a haloalkane for astatine?

I'm studying organic chemistry, and I noticed that there are fluoro-, chloro-, bromo-, and iodoalkanes. However, there are none for Astatine. Could someone shed some light on this, and what it would ...
13
votes
1answer
2k views

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 ...
13
votes
1answer
5k views

Why use potassium iodide instead of copper iodide in Sandmeyer reaction?

The Sandmeyer reaction is an extremely useful reaction for the functionalization of aromatic rings through a diazonium intermediate. For conversion of a diazonium intermediate to the corresponding ...
13
votes
1answer
256 views

Does (2-fluoroethyl)benzene undergo elimination via E1cb or E2?

I have seen in two different sources claiming that $\ce{PhCH2CH2F}$ gives styrene $\ce{PhCH=CH2}$ when treated with alcoholic $\ce{KOH}$, but one source suggests an E1cb mechanism, while the other ...
12
votes
2answers
2k views

Bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine

Write the mechanism for the following reaction (bromination of 1,3,5-cyclooctatriene followed by nucleophilic substitution by excess dimethylamine): My answer so far: I have only shown one of ...
12
votes
4answers
8k views

Will this beta-branched secondary alkyl halide undergo SN1 or SN2?

What is the correct mechanism here? Would SN1 occur here? I chose SN2 because we have a secondary alkyl halide with a weak base $\ce{CN-}$. However, the solution says SN1 is major. Can you explain ...
12
votes
1answer
669 views

Existence of Dichlorine Pentoxide

I searched the net and a lot of books, but I was unable to find any information about dichlorine pentoxide. Does dichlorine pentoxide($\ce{Cl2O5}$) exist? If it doesn't exist, then why so? If ...
12
votes
1answer
566 views

Why does a six-membered ring contract in this SN1 reaction?

I was watching this video on Khan Academy (YouTube link) regarding SN1 mechanisms and carbocation rearrangements and came across this mechanism. At around timestamp 4:20 in the video, why does step 2 ...
12
votes
1answer
157 views

Products formed on cleavage of epoxides using HI

There seems to be multiple forms of HI used to cleave epoxides: conc. HI, anhydrous HI, cold HI, hot HI, cold conc. HI, hot conc. HI, etc. So, does concentration of HI and temperature have any ...
11
votes
1answer
814 views

Friedel–Crafts alkylation of benzene with tetrachloromethane

There was this question in an exam at our school which asked what the major product will be when excess of benzene is reacted with tetrachloromethane in the presence of aluminium chloride. All of us ...
11
votes
2answers
820 views

N-fluorosuccinimide: any scope?

All halogen derivatives (except fluorine) of succinimide exist and are used in various chemical processes. What makes N-fluorosuccinimde difficult to prepare? Still chemists have not been able to ...
11
votes
1answer
930 views

In the Favorskii rearrangement, why doesn't the base grab the alpha hydrogen of the carbon bearing the halogen?

In the Favorskii rearrangement, the base (like hydroxide) always abstracts the alpha hydrogen of the carbon not bearing the halogen. But to me the hydrogens on the carbon directly connected to the ...
11
votes
1answer
948 views

Why is KI oxidized by H2SO4, whereas NaBr isn't oxidised?

My textbook says that alcohols react with sodium bromide and sulphuric acid to form the corresponding alkyl bromides. At the same time they also mention that sulphuric acid mustn't be used with ...
11
votes
1answer
2k views

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 ...
11
votes
1answer
658 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 ...
10
votes
1answer
555 views

Geometry of the pentachloridoindate(III) anion

According to Brown et al.,1 the crystal structure of $\ce{[NEt4]2[InCl5]}$ reveals that the pentachloridoindate(III) anion, $\ce{[InCl5]^2-}$, adopts a square pyramidal $C_\mathrm{4v}$ geometry (VSEPR ...
10
votes
1answer
10k views

How to rationalise the planar structre of I2Cl6?

$\ce{I2Cl6}$ is a dimer of $\ce{ICl3}$. $\ce{ICl3}$ is T-shaped, with $\ce{I}$ being $\mathrm{sp^3d}$ and having two lone pairs. I read in Inorganic Reaction Mechanisms by R. K. Sharma that $\ce{...
10
votes
1answer
227 views

Why doesn't tetraiodine exist?

I've run into a question that says after doing the Lewis structure of $\ce{IF3}$, which I did, explain why $\ce{I4}$ doesn't exist. I am confused as to how it can be explained. I've thought that ...
10
votes
1answer
4k 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) ...
10
votes
2answers
568 views

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

Recently I came across this question and in the comment section, there was an argument regarding the formula of sodium hypoiodite which kept me wandering: what is the actual formula of alkali ...
10
votes
1answer
728 views

Mechanism of lithium-halogen exchange of primary alkyl iodide

On Clayden's page 190 this reaction is given for preparation of organometallics: What is the mechanism of this reaction? I expected the "almost carboanion" part of the $\ce{t-BuLi}$ to attack as a ...
10
votes
1answer
8k views

What is the structure of iodide of Millon's base?

In qualitative analysis, $\ce{NH4+}$ ions are confirmed using Nessler's reagent:- $$\ce{NH4+ + 2[HgI4]^{2−} + 4OH− → HgO·Hg(NH2)I ↓ + 7I^{−} + 3H2O}$$ The brown precipitate ...
9
votes
1answer
1k views

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 ...
9
votes
1answer
837 views

Why don't hydride shifts occur with hydrohalogenation of 4-methyl-cyclohexene?

My book (see bottom) implies that hydrohalogenation of 4-methyl-cyclohexene follows this mechanism: Why not undergo consecutive hydride shifts to furnish a tertiary carbocation? I would guess that ...
8
votes
2answers
13k views

Why is thionyl chloride preferred for preparing alkyl chlorides from alcohols?

Why is thionyl chloride ($\ce{SOCl2}$) preferred for preparing alkyl chlorides from alcohols, as opposed to say $\ce{PCl5}$ or $\ce{PCl3}$ ?
8
votes
2answers
1k views

Why does chlorination of toluene stop at two chlorine atoms?

My instructor mentioned a reaction for preparation of benzaldehyde by chlorination of toluene in presence of sunlight to form benzal dichloride, which on hydrolysis gives benzaldehyde. However, I'm ...