Interhalogen Compounds: Classification, Structure and Example

Edited By Shivani Poonia | Updated on Jul 02, 2025 07:08 PM IST

Interhalogen compounds are very a hot area of chemistry that is a result of the combination of two halogen atoms that react into distinct molecules containing particular properties. Everyday items include species that are formed by the reaction of the halogens that mention the compounds of Group 17 of the periodic table, inclusive of fluorinated compounds classified as reacting and interhalogens, which are stable. Understanding interhalogen compounds is very key for a student or chemist and to any application, of course, in the daily life of general interest. A paper of this kind will much detail give the definition and the key features of interhalogens.

This Story also Contains

Physical Properties of Group 13 - 1
Preparation
Physical Properties of Group 13 — 2
Summary

Interhalogen Compounds: Classification, Structure and Example

Physical Properties of Group 13 - 1

While most of these interhalogens have their physical properties contrasting to one another, it is the only thing that shows their specific configuration.

They normally have low boiling as well as melting points in most cases compared to their corresponding halogen elements. The molecular size and the nature of the bonding of the interhalogens have resulted in different volatilities and stability. Most of the interhalogen compounds are gases or liquid in normal room temperatures which is in complete contrast to the halogens that exist as solids. Again, this is revealed by the specific halogens that are involved in the molecule. For example, interhalogens containing fluorine are normally most easily reacted upon. They also exhibit varying behavior in solubility as compared to those containing iodine. These physical behaviors thus become important to enable imagination of how the interhalogens will behave under a particular reaction and hence industrial use of the interhalogens.

When two different halogens react with each other, interhalogen compounds are formed. They can be assigned general compositions as XX′, XX₃′, XX₅′, and XX₇′ where X is halogen of larger size and X′ of smaller size, and X is more electropositive than X′. As the ratio between radii of X and X′ increases, the number of atoms per molecule also increases. Thus, iodine (VII) fluoride should have a maximum number of atoms as the ratio of radii between I and F should be maximum. That is why its formula is IF₇ (having a maximum number of atoms).

Preparation

The interhalogen compounds can be prepared by the direct combination or by the action of halogen on lower interhalogen compounds. The product formed depends upon some specific conditions, For example,

$\begin{aligned} & \mathrm{Cl}_2+\mathrm{F}_2 \xrightarrow{437 \mathrm{~K}} 2 \mathrm{ClF} \\ & \mathrm{I}_2+3 \mathrm{Cl}_2 \rightarrow 2 \mathrm{ICl}_3\end{aligned}$

Properties

Some properties of interhalogen compounds are given in the following table.

These are all covalent molecules and are diamagnetic in nature. They are volatile solids or liquids at 298 K except ClF which is a gas. Their physical properties are intermediate between those of constituent halogens except that their m.p. and b.p. are a little higher than expected.
Their chemical reactions can be compared with the individual halogens. In general, interhalogen compounds are more reactive than halogens (except fluorine). This is because the X–X′ bond in interhalogens is weaker than the X–X bond in halogens except the F–F bond. All these undergo hydrolysis giving halide ion derived from the smaller halogen and a hypohalite ( when XX′), halite (when XX′₃), halate (when XX′₅), and perhalate (when XX′₇) anion derived from the larger halogen.

$\mathrm{XX}^{\prime}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{HX}^{\prime}+\mathrm{HOX}$

Their molecular structures are very interesting and can be explained on the basis of VSEPR theory. The XX₃ compounds have the bent ‘T’ shape, XX₅ compounds are square pyramidal, and IF₇ has pentagonal bipyramidal structures.

Physical Properties of Group 13 — 2

Physical properties, by themselves, also play a role in the reactivity and stability of inter-halogen compounds. The potential with compounds having dipole-dipole interaction presents different reactivity. Lone pairs on the central atom, and differences in electronegativity between the halogens, will themselves constitute determinant features for the molecular geometry that affects the chemical behavior.

Hence, these characteristics of their nature exert intermolecular forces between the atoms of interhalogen compounds: this can change their behavior under physical states and phases, often very beneficial in some sorts of applications.

For example, some of the interhalogen compounds can be exploited in the form of an oxidizing agent, while others can be utilized in selective organic synthesis cases as a halogenating agent. Knowing these properties not only helps in laboratory practices but also reveals treasures hidden behind their importance for technological applications. Relevance and Applications of Interhalogen Compounds

Interhalogen compounds are very important in strong character not only in an academic research field but also in applications. They are very important in synthetic chemistry due to their unique reactivity in synthesizing elements into more complex molecules and even in a reaction mechanism of said molecule. For instance, some interhalogen is used to make organohalides constituting intermediates for agrochemicals and pharmaceuticals.

Furthermore, it is possible to synthesize from these compounds some advanced materials, especially on polymers and fluorinated substances, with exceptional properties of higher strength and thermal resistance. The use of interhalogens having a number of limited compounds in the sphere of environmental science has been known from their possibilities of involvement in cleaning pollution through the processing of waste raw materials.

Industrially, these compounds are used in disinfectants and cleaning agent applications since they show good biocidal activity. These compounds have an important role in our daily life, from house applications to industry.

Summary

The interhalogen compounds are interesting chemical species that unitize the different varieties of halogens. Their unique physical properties reactivity and applicability in real-life situations made them pretty much a significant aspect in relation to both the academic chemistry system, announced earlier, and the practical application systems nowadays. The author of this paper gives a description about the basics of interhalogen compounds, more specifically physical properties and types, and areas of application.

Frequently Asked Questions (FAQs)

1. 1. What do interhalogen compounds involve?

Interhalogen compounds involve various halogens concerning self-reaction with others, resulting in the formation of molecular species within a unique property category. For example, ClF and BrF₃ ICl should all be relevant to a great many important chemical reactions and utility.

2. 2. Physical Properties of Interhalogen Compounds:

Interhalogen compounds generally exhibit low boiling and melting points. They are characterized by volatility and varying solubility, depending on the nature of the atoms involved in the compound. They exist in the form of either gas, liquid, or solid at room temperature. The above variation depends on the size of molecular size and intermolecular forces acquired by the compound.

3. 3. Some general uses of interhalogen compounds in any industry are:

They also apply to several industrial uses. In the pharmaceutical industry, they are used in the synthesis of halogenated intermediates important in synthesizing several drugs. In material science, interhalogens find use in developing emerging polymers with unusual properties. Not to forget, they find a place in environmental science, in waste treatment solutions for neutralizing pollutants.

4. 4. Why is interhalogen compound reactivity important?

The interhalogen compounds are of a highly reactive nature and hence help in most chemical reactions. Scoring on these specifications, interhalogen compounds get involved in quite a good number of reactions regarding organic synthesis for the preparation of halogenated products and as oxidizing agents in the case of some special applications. They stand with good importance to be used in research and industrial use also.

5. 5. Can interhalogen compounds prove harmful?

These are interhalogen compounds known to be reactive, so they can turn hazardous if taken beyond their capacity to be toxic. Proper care and precautions, like work wearing laboratory and industrial personal protective equipment in areas with proper ventilation, should always be taken.

6. Why is ClF3 bent while BF3 is planar?

ClF3 is bent while BF3 is planar due to the presence of lone pairs on the central chlorine atom in ClF3. These lone pairs occupy space and repel the bonding pairs, resulting in a bent structure. BF3, on the other hand, has no lone pairs on the central boron atom, allowing for a planar trigonal structure.

7. How does the bond length in interhalogen compounds compare to that of pure halogens?

The bond length in interhalogen compounds is generally shorter than the average of the bond lengths in the pure halogens. This is due to the partial ionic character of the bond resulting from the electronegativity difference between the two halogens.

8. How does the melting point of interhalogen compounds compare to that of pure halogens?

Interhalogen compounds generally have higher melting points than pure halogens. This is due to the stronger intermolecular forces resulting from the polar nature of interhalogen bonds, which require more energy to overcome during melting.

9. Why can't all halogens form all types of interhalogen compounds?

Not all halogens can form all types of interhalogen compounds due to size limitations and electronic configurations. Larger halogens (like iodine) can accommodate more bonds, forming AX5 and AX7 compounds, while smaller halogens (like fluorine) are limited to AX or AX3 types.

10. Why are most interhalogen compounds more reactive than pure halogens?

Most interhalogen compounds are more reactive than pure halogens because of their polar nature and the weakness of the A-X bond compared to X-X bonds. The polarity makes them better electrophiles, while the weaker A-X bond makes them more susceptible to bond cleavage.

11. How does electronegativity affect the formation of interhalogen compounds?

Electronegativity plays a crucial role in interhalogen compound formation. The more electronegative halogen (usually fluorine) attracts electrons more strongly, forming a polar covalent bond with the less electronegative halogen. This difference in electronegativity contributes to the compound's stability and reactivity.

12. What determines the central atom in an interhalogen compound?

The central atom in an interhalogen compound is always the larger, less electronegative halogen. This is because the larger atom can accommodate more bonds and has more available orbitals for bonding.

13. How does the structure of AX type interhalogen compounds differ from diatomic halogens?

AX type interhalogen compounds have a linear structure similar to diatomic halogens, but with two different halogen atoms. The bond in interhalogen compounds is more polar due to the electronegativity difference, unlike the non-polar bonds in diatomic halogens.

14. How are interhalogen compounds classified?

Interhalogen compounds are classified based on their composition into four types: AX, AX3, AX5, and AX7, where A represents the less electronegative halogen and X represents the more electronegative halogen.

15. What is the general trend in reactivity among interhalogen compounds?

The reactivity of interhalogen compounds generally increases with an increase in the number of X atoms. This means AX7 compounds are typically more reactive than AX5, which are more reactive than AX3, and so on. This trend is due to the increased polarity and instability of compounds with more X atoms.

16. What is the importance of interhalogen compounds in organic synthesis?

Interhalogen compounds are important in organic synthesis as halogenating agents. They can introduce halogen atoms into organic molecules more selectively and under milder conditions than pure halogens. For example, ICl is used for iodination of aromatic compounds.

17. Why are some interhalogen compounds used as fluorinating agents?

Some interhalogen compounds, particularly those containing fluorine (like ClF3 or BrF3), are used as fluorinating agents because they can readily release fluorine atoms. The strong oxidizing power and the weakness of the A-F bond make these compounds effective for introducing fluorine into other molecules.

18. What are interhalogen compounds?

Interhalogen compounds are chemical substances formed by the combination of two different halogen elements. They consist of a more electropositive halogen bonded to a more electronegative halogen, resulting in unique properties that differ from pure halogens.

19. How does the reactivity of interhalogen compounds with water compare to that of pure halogens?

Interhalogen compounds generally react more vigorously with water than pure halogens. This is due to their higher polarity and reactivity. The reaction often results in disproportionation, producing oxyacids of both halogens involved.

20. How does the concept of hypervalency apply to interhalogen compounds?

Hypervalency is relevant to interhalogen compounds, particularly those involving larger central atoms like iodine. These atoms can expand their octet, accommodating more than eight electrons in their valence shell. This allows for the formation of compounds like IF7, where iodine forms seven bonds.

21. How does the VSEPR theory explain the structure of IF7?

VSEPR (Valence Shell Electron Pair Repulsion) theory explains the structure of IF7 as pentagonal bipyramidal. The central iodine atom forms seven bonds with fluorine atoms, arranging themselves to minimize electron pair repulsion. Five F atoms form a pentagonal plane, while two F atoms occupy axial positions above and below this plane.

22. What is the hybridization of the central atom in ICl5?

In ICl5, the central iodine atom undergoes sp3d2 hybridization. This hybridization allows for the formation of five bonds and accommodates one lone pair, resulting in a square pyramidal molecular geometry.

23. What is the significance of the term "hypervalent" in relation to some interhalogen compounds?

The term "hypervalent" is significant for some interhalogen compounds because it describes central atoms that appear to have more than eight electrons in their valence shell. This concept explains the existence of compounds like IF7, where iodine forms more bonds than would be predicted by the octet rule.

24. What role do interhalogen compounds play in atmospheric chemistry?

Interhalogen compounds play a significant role in atmospheric chemistry, particularly in ozone depletion. Compounds like ClONO2 (chlorine nitrate) are involved in catalytic cycles that destroy ozone in the stratosphere. Understanding these compounds is crucial for environmental science and climate studies.

25. How do interhalogen compounds contribute to the understanding of molecular orbital theory?

Interhalogen compounds provide valuable examples for understanding molecular orbital theory. The bonding in these compounds, especially in more complex structures like IF7, demonstrates concepts such as hybridization, multiple bond formation, and the role of d-orbitals in bonding, enhancing our understanding of molecular orbital interactions.

26. What is the significance of the "banana bond" in certain interhalogen compounds?

The "banana bond" or bent covalent bond is significant in certain interhalogen compounds like ClF3. It results from the overlap of p orbitals at an angle, rather than head-on, due to the presence of lone pairs. This unique bonding contributes to the compound's reactivity and structural properties.

27. How does the oxidizing power of interhalogen compounds compare to that of halogens?

Interhalogen compounds are generally stronger oxidizing agents than the pure halogens they're composed of (except for fluorine). This is due to the polar nature of the A-X bond, which makes the X atom more electrophilic and thus a better oxidizing agent.

28. Why is IF7 stable but CF7 does not exist?

IF7 is stable while CF7 does not exist due to the difference in atomic size and available orbitals. Iodine, being larger, can expand its octet and accommodate seven bonds using its d orbitals. Carbon, being smaller and lacking d orbitals, cannot expand its octet to form seven bonds.

29. How does the dipole moment of interhalogen compounds affect their properties?

The dipole moment in interhalogen compounds, resulting from the electronegativity difference between the halogens, affects various properties. It increases solubility in polar solvents, enhances reactivity, and influences intermolecular forces, affecting boiling and melting points.

30. What role does atomic size play in the formation of different types of interhalogen compounds?

Atomic size plays a crucial role in determining which types of interhalogen compounds can form. Larger halogens like iodine can form AX5 and AX7 compounds because they have more space to accommodate multiple X atoms. Smaller halogens like chlorine are limited to AX or AX3 types due to spatial constraints.

31. How does the nature of bonding in interhalogen compounds affect their conductivity?

The nature of bonding in interhalogen compounds, which is predominantly covalent with some ionic character, results in poor electrical conductivity in their pure state. However, when dissolved in polar solvents, they can conduct electricity due to partial ionization.

32. What is the significance of the T-shaped structure in some interhalogen compounds?

The T-shaped structure, seen in compounds like ClF3, is significant because it demonstrates the effect of lone pairs on molecular geometry. Two lone pairs occupy equatorial positions, forcing the three bonds into a T-shape. This structure influences the compound's reactivity and physical properties.

33. How do interhalogen compounds participate in Lewis acid-base reactions?

Interhalogen compounds can act as Lewis acids due to the electron-deficient nature of the central atom. They can accept electron pairs from Lewis bases, forming adducts. For example, ICl can form ICl3- by accepting a pair of electrons from a chloride ion.

34. Why are some interhalogen compounds considered pseudohalogens?

Some interhalogen compounds are considered pseudohalogens because they exhibit properties similar to halogens, such as forming anions similar to halide ions. For example, ICl can form I+ and Cl- ions in solution, mimicking the behavior of halogens.

35. How does the bond angle in interhalogen compounds vary with the number of X atoms?

The bond angle in interhalogen compounds generally decreases as the number of X atoms increases. For example, the F-Cl-F angle in ClF3 is about 87.5°, while in ClF5, the equatorial F-Cl-F angle is about 84.8°. This is due to increased electron pair repulsion with more bonds.

36. How does the stability of interhalogen compounds change across a period in the periodic table?

The stability of interhalogen compounds generally decreases across a period in the periodic table. For example, ClF is more stable than BrF, which is more stable than IF. This trend is due to the decreasing electronegativity difference between the halogens as we move across the period.

37. Why do interhalogen compounds often have a higher boiling point than expected?

Interhalogen compounds often have higher boiling points than expected due to increased intermolecular forces. The polar nature of these compounds leads to stronger dipole-dipole interactions, requiring more energy to overcome these forces and transition to the gas phase.

38. What is the relationship between the structure of interhalogen compounds and their dipole moments?

The structure of interhalogen compounds directly influences their dipole moments. Linear AX compounds have a dipole moment due to the electronegativity difference. However, symmetrical structures like AX4 (tetrahedral) or AX6 (octahedral) have zero net dipole moment despite polar individual bonds, due to cancellation of dipoles.

39. How do interhalogen compounds interact with noble gases?

Some interhalogen compounds, particularly those containing fluorine, can react with noble gases to form compounds. For example, XeF2 can be formed by the reaction of xenon with fluorine. This interaction is possible due to the high electronegativity of fluorine and the relatively large size of heavier noble gases.

40. Why are interhalogen compounds often stored in special containers?

Interhalogen compounds are often stored in special containers due to their high reactivity and corrosive nature. Many of these compounds react vigorously with water and organic materials. Containers made of materials like Teflon or certain metals that resist corrosion are used to safely store these reactive substances.

41. How does the presence of d-orbitals in the central atom affect the formation of interhalogen compounds?

The presence of d-orbitals in the central atom allows for the formation of higher-order interhalogen compounds like AX5 and AX7. Elements like iodine can use their d-orbitals to expand their octet and form additional bonds. This is why iodine can form compounds like IF7, while chlorine is limited to ClF3.

42. How do interhalogen compounds compare to interhalogens in terms of structure and properties?

Interhalogen compounds and interhalogens are the same thing - these terms are used interchangeably. They refer to compounds formed between two different halogen elements, exhibiting unique structures and properties that differ from pure halogens due to the electronegativity difference between the constituent halogens.

43. Why do some interhalogen compounds exhibit geometric isomerism?

Some interhalogen compounds exhibit geometric isomerism due to the arrangement of different halogen atoms around the central atom. For example, BrF5 can exist in two forms: square pyramidal and trigonal bipyramidal. This isomerism arises from the different possible arrangements of the lone pair and bonding pairs of electrons.

44. How does the concept of HSAB (Hard and Soft Acids and Bases) apply to interhalogen compounds?

The HSAB concept applies to interhalogen compounds in their reactions. Generally, the larger, less electronegative halogen acts as a softer Lewis acid, while the smaller, more electronegative halogen acts as a harder base. This principle helps predict the reactivity and stability of different interhalogen compounds.

45. How do interhalogen compounds interact with transition metals?

Interhalogen compounds can interact with transition metals to form complex compounds. The more electronegative halogen often bonds to the metal, while the less electronegative one may be displaced. For example, PtCl4 reacts with excess IF to form PtF6, demonstrating the strong fluorinating ability of IF.

46. Why are some interhalogen compounds considered better halogens than others for certain reactions?

Some interhalogen compounds are considered better halogenating agents than others for certain reactions due to their specific reactivity and selectivity. For instance, ICl is often preferred for aromatic iodination because it's less reactive than I2, allowing for more controlled and selective halogenation.

47. How does the concept of electronegativity inversion apply to some interhalogen compounds?

Electronegativity inversion occurs in some interhalogen compounds where the normally less electronegative atom becomes more electronegative due to its oxidation state. For example, in IF7, the central iodine atom, due to its high oxidation state, can be considered more electronegative than the surrounding fluorine atoms.

48. What is the significance of the "3c-4e" (three-center-four-electron) bond in some interhalogen compounds?

The "3c-4e" bond is significant in some interhalogen compounds like I3-. This bonding involves three atoms sharing four electrons, resulting in a delocalized bond. It explains the stability and linear structure of such ions, which cannot be adequately described by traditional two-center two-electron bonds.

49. Why do some interhalogen compounds exhibit unusual oxidation states?

Some interhalogen compounds exhibit unusual oxidation states due to the high electronegativity of halogens, particularly fluorine. For example, in IF7, iodine has an oxidation state of +7, which is higher than its typical maximum of +5. This is possible because fluorine can induce high oxidation states in other elements.

50. How does the reactivity of interhalogen compounds change with temperature?

The reactivity of interhalogen compounds generally increases with temperature. Higher temperatures provide more energy to overcome activation barriers, leading to faster reaction rates. However, some interhalogen compounds may decompose at elevated temperatures, so temperature control is crucial in their handling and reactions.

51. What is the importance of interhalogen compounds in inorganic synthesis?

Interhalogen compounds are important in inorganic synthesis as powerful halogenating and oxidizing agents. They can introduce halogens into molecules under milder conditions than elemental halogens. For example, BrF3 is used to prepare metal fluorides that are difficult to obtain by direct fluorination with F2.

52. How do interhalogen compounds interact with pi-electron systems?

Interhalogen compounds can interact with pi-electron systems through electrophilic addition reactions. The more electropositive halogen often acts as the elect