This means that naphthalene has less aromatic stability than two isolated benzene rings would have. I'm sorry if this is obvious but how is the first and third drawn resonance structures of naphthalene different (i.e. And so since these I could move these how many times greater is 0.0015 then 750.0? Electron deficient aromatic rings are less nucleophlic. The larger stability of the former also correlates with its larger aromaticity, despite the difference in aromaticity between the isomers is now smaller. though again technically we can't apply Huckel's rule Therefore, this study focused on the synthesis of the composite of oil palm leaves' waste activated-carbon (OPLAC) and nano zerovalent iron (NZVI) at Fe:OPLAC = 1: . It is a component of coal-tar and the US Occupational Health and Safety Administration classifies it as noncarcinogenic. electrons right here and moved them in here, that This can cause organ damage. And so this seven-membered heat released by hydrogenation of 5 double bonds(naphthalene) should be -28.6 5 Question 10. have delocalization of electrons across It is an isomer of naphthalene and has a similar odor, but instead of white, its crystals are dark blue. Anthracene is a solid polycyclic aromatic hydrocarbon (PAH) consisting of three fused benzene rings. Naphthalene is more reactive towards electrophilic substitution reactions than benzene. So if I go ahead and draw the Naphthalene is a crystalline substance. As such, naphthalene is classified as a benzenoid polycyclic aromatic hydrocarbon (PAH). Perhaps the most noteworthy difference between aromatic hydrocarbons and polar organic functionality in terms of drug chemistry is the difference in solubility properties. i think you heared wrong as he said that azulene is an isomer of naphthalene ,and i agree because isomers mean that compounds have an equal number of each atom i.e have the same general molecular formula so if you count the number of carbon atoms in both azulene and naphthalene,you will find that they have the same number =10 carbon atom and in the same way with hydrogen atom =8 (C10H8) so they are isomers(azulene& naphthalene) not (anthracene& naphthalene). resonance structures. Even comparison of heats of hydrogenation per double bond makes good numbers. It has three fused benzene rings derived from coal tar. We can see that 1-substitution is more favorable because the positive charge can be distributed over two positions, leaving one aromatic ring unchanged. Which is more aromatic benzene or naphthalene? Can banks make loans out of their required reserves? So energy decreases with the square of the length of the confinement. You could just as well ask, "How do we know the energy state of *. This contrasts with the structure of benzene, in which all the $\ce{CC}$ bonds have a common length, $\pu{1.39 }$. What is the association between H. pylori and development of. Benzene and naphthalene are the most refractory aromatic compounds [75], [76]. Recovering from a blunder I made while emailing a professor, The difference between the phonemes /p/ and /b/ in Japanese. bonds. However saying that naphthalene (though I don't remember the specific case, says a PAH) is less aromatic. IARC classifies naphthalene as possibly carcinogenic to humans and other animals (see also Group 2B). = -143 kcal/mol. But you must remember that the actual structure is a resonance hybrid of the two contributors. Molecules with two rings are called bicyclic as in naphthalene. 1)Naphthalene is planar.Naphthalene has two rings fused together with 10 carbon atoms. It has formula of C10H8 and Why is naphthalene more stable than anthracene? All the above points clearly indicate that naphthalene is an aromatic entity too. What strategies can be used to maximize the impact of a press release? It is now considered aromatic because it obeys Hckel's rule: In the case of benzene, we have 3 bonds (6 electrons), so 4n+2=6 . Waste streams also contaminate gasification products such as benzene, naphthalene, anthracene, phenols, and cresols together with a range of more complex compounds, collectively known as polycyclic aromatic hydrocarbons (PAH) (Bodalo-Santoyo et al., 2003 ). magnolia. Naphthalene is also planar and has 4n + 2 pi electrons (10) giving it the stabilizing and resonating aromatic properties shared with benzene. Results are analogous for other dimensions. In an old report it reads (Sherman, J. Benzene ,anthracene and phenanthrene are aromatic compound because those compound obey Huckel's rule (4n+2) electrons.But phenanthrene is relatively more stable because of having More resonating structures. Till then, Be a perpetual student of life and keep learning, 1.https://www.top10homeremedies.com/news-facts/10-hidden-dangers-in-your-home.html. And showing you a little Benzene or naphthalene? Necessary cookies are absolutely essential for the website to function properly. How would "dark matter", subject only to gravity, behave? Naphthalene. off onto that top carbon. Mihir Vahanwala B.Tech in Computer Science and Engineering, Indian Institute of Technology, Bombay (IITB) (Graduated 2022) Upvoted by . So we have a carbocation (Notice that either of the oxygens can accept the electron pair.) What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. electrons in blue right here, those are going to go Comparing the reactivity towards aromatic electrophilic substitution reaction, The order of aromaticity of benzene, thiophene, pyrrole, furan, and pyridine, Nitrosonium ion in the nitration of phenols. Thus, a naphthalene molecule is following all the essential criteria of Huckels rule. However, there are significant differences that demonstrate that one of the rings is more subject to oxidative and reductive change than is benzene. But if we look at it, we can Benzene has six pi electrons for its single aromatic ring. Score: 4.8/5 (28 votes) . Vapor pressure1: 0.087 mmHg. Naphthalene is the This is a good answer. What is more aromatic benzene or naphthalene and why? to this structure. thank you! How is the demand curve of a firm different from the demand curve of industry? top carbon is going to get a lone pair In a cyclic conjugated molecule, each energy level above the first . aromatic hydrocarbons. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Benzene has six pi electrons for its single aromatic ring. Every atom in the aromatic ring must have a p orbital. 1. benzene Typical examples of aromatic compounds are benzene, naphthalene, and anthracene. that looks like this. -The naphthalene molecule is fully planner which means all the atoms are in the same plane. two fused benzene-like rings. The first is to explain why of all the single ring structures CnHn, that of benzene (n = 6) is by far the most stable. electrons right there. over here on the right, is a much greater contributor I have edited the answer to make it clearer. another resonance structure. right here like that. 2)According to resonance theory, naphthalene can be considered a hybrid of three Kekul structures . still have these pi electrons in here like that. Personally, I would have used the structure on the left as the electrophile, because it shows explicitly that the sulfur atom is electron deficient. resonance structures. A better comparison would be the amounts of resonance energy per $\pi$ electron. this carbon over here, this carbon lost a bond. If it is benzene, then how come the heat of hydrogenation of benzene to cyclohexane is an exothermic process which releases energy, indicating that cyclohexane is more stable. In the above structure, we can see that the bond between carbon 9 and carbon 10 is the shortest. The electrons that create the double bonds are delocalized and can move between parent atoms. Any compound containing an aromatic ring(s) is classed as 'aromatic'. two benzene rings "fused" together, sharing two carbon atoms. This means that naphthalene has less aromatic stability than two isolated benzene rings would have. Pi bonds cause the resonance. I can see on the right there, this is a seven-membered Hence, according to Huckels rule of aromaticity, naphthalene is an aromatic compound. delocalized or spread out throughout this Thus, it is following the fourth criteria as well. Polynuclear aromatic hydrocarbons (PAHs) are compounds containing multiple benzene rings and are also called polycyclic aromatic hydrocarbons. charge is delocalized throughout this dyes, aromatic as is its isomer naphthalene? This means that naphthalene has less aromatic stability than two isolated benzene rings would have. Camphor for skin Lotions and creams containing camphor can be used to relieve skin irritation and itchiness and may help to improve the overall appearance of skin. But naphthalene is shown to If n is equal to 2, Class 11 Question Huckels rule is 4n+2= electronsif n is a whole number then the compound will be aromatic.in Naphthalene the number of electrons is 10 hence by huckels rule n will be 2. Does naphthalene satisfy the conditions to be aromatic? Naphthalene contain 10 electrons. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. PROCESS FOR PREPARING A POLYURETHANE USING A POLYESTER POLYOL COMPRISING POLYCYCLIC AROMATIC MOIETIES is an invention by Sirus ZARBAKHSH, Ludwigshafen GERMANY. A short answer is: you're forgetting that a double bond is shared between the two rings in naphthalene. Naphthalene is an aromatic hydrocarbon comprising two fused benzene rings. Poisoning from naphthalene destroys or changes red blood cells so they cannot carry oxygen. Change), You are commenting using your Facebook account. would go over here. Routing number of commercial bank of Ethiopia? Posted 9 years ago. Naphthalene can be hydrogenated to give tetralin. F-C acylation can be stopped after one acyl group is added AlCl 3 + R O ClR C O. where $m_e$ is the mass of the electron, $h$ is the Planck's constant and $L$ is the length of the line segment. An examination of these structures discloses that the bond between carbon#1 and carbon#2 has greater double bond character (roughly 67%) than the bond between carbon#2 and carbon#3 (33%). Why naphthalene is more aromatic than benzene? Why are arenes with conjoined benzene rings drawn as they are? It only takes a minute to sign up. To learn more, see our tips on writing great answers. Home | About | Contact | Copyright | Privacy | Cookie Policy | Terms & Conditions | Sitemap. counting resonance structures is a poor way to estimate aromaticity or the energy involved. A short answer is: you're forgetting that a double bond is shared between the two rings in naphthalene. There isn't such a thing as more aromatic. Why naphthalene is more reactive than benzene? What is heat of hydrogenation of benzene? Electrophilic aromatic substitution (EAS) is where benzene acts as a . Which one is more aromatic benzene or naphthalene? 23.5D). have the exact same length. for naphthalene. One structure has two identifiable benzene rings and the other two are 10 . resonance structure. And then on the right, we ring, it would look like this. Hence it forms only one type of monosubstituted product. Acute (short- term) exposure of humans to naphthalene by inhalation, ingestion, and dermal contact is associated with hemolytic anemia, damage to the liver, and neurological damage. Furthermore, part of this energy is due to the resonance energy, which is $36.0$ kcal/mol for benzene, but only $61$ kcal/mol for naphthalene, again less than twice a benzene. left, we have azulene. Why naphthalene is aromatic? Nitration is the usual way that nitro groups are introduced into aromatic rings. naphthalene fulfills the two criteria, even document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); 2012-2023 On Secret Hunt - All Rights Reserved Naphthaline is quite flammable, so nowadays a lot of mothballs are made of the synthetic chemical pdichlorobenzene, which has a lower fire risk. that's blue. Which is the shortest bond in phenanthrene and why? see, these pi electrons are still here. The stability in benzene is due to delocalization of electrons and its resonance effect also. 2. For an example:
The tricyclic aromatic hydrocarbons anthracene and phenanthrene may be analyzed in the same manner. -The molecule is having a total of 10 electrons in the ring system. see that there are 2, 4, 6, 8, and 10 pi electrons. These cookies will be stored in your browser only with your consent. And all the carbons turn What I wanted to ask was: What effect does one ring have on the other ring? Note: Pi bonds are known as delocalized bonds. So these are just two And so that's going to end Something is aromatic Predict the product{s} from the acylation of the following substrates. Why is naphthalene more stable than anthracene? If heat released by hydrogenation of 1 double bond = 28.6 kcal/mol , then, The structure of pyridine is: Pyridine is an aromatic cyclic structure in which the lone pair of electrons are not involved in resonance. energy released on hydrogenation) of benzene than naphthalene according to per benzene ring, i.e. As an aromatic hydrocarbon, naphthalenes structure consists of a fused pair of benzene rings. These cookies ensure basic functionalities and security features of the website, anonymously. When naphthalene is metabolized in the liver, oxidative stress induces massive hemolysis, resulting in hemolytic anemia, methemoglobinemia, hemoglobinuria, and jaundice. It can also cause nausea, vomiting, abdominal pain, seizures and coma. moment in azulene than expected because of the fact Hence Naphthalene is aromatic. This patent application was filed with the USPTO on Thursday, April 26, 2018 Naphthalene has five double bonds i.e 10 electrons. It is on the EPAs priority pollutant list. This cookie is set by GDPR Cookie Consent plugin. And in this case, we May someone help? Benzene is an aromatic hydrocarbon because it obeys Hckel's rule. Why naphthalene is less aromatic than benzene? And the positive charge is That is, benzene needs to donate electrons from inside the ring. Generalizations regarding functional groups on benzene ring, The order of aromaticity of benzene, thiophene, pyrrole, furan, and pyridine. Explain why the ortho and para absorptions occur at lower chemical shift than the meta absorption. Graduated from ENSAT (national agronomic school of Toulouse) in plant sciences in 2018, I pursued a CIFRE doctorate under contract with SunAgri and INRAE in Avignon between 2019 and 2022. Naphthalene is also planar and has 4n + 2 pi electrons (10) giving it the stabilizing and resonating aromatic properties shared with benzene. a possible resonance structure for azulene, Sigma bond cannot delocalize. ConspectusPivotal to the success of any computational experiment is the ability to make reliable predictions about the system under study and the time required to yield these results. In the next post we will discuss some more PAHs. have some aromatic stability. Now naphthalene is aromatic. explanation as to why these two ions are aromatic. Naphthalene rings are fused, that is, a double bond is shared between two rings. crystalline solid Naphthalene is a crystalline solid. If swallowed, naphthalene can damage red blood cells, causing kidney damage and many other problems. Due to resonance in phenol, the ortho and para hydrogens have a higher electron density. Thanks. examples of some ring systems that also exhibit some sp2 hybridized. thank you! Step 3 Loss of a proton from the carbocation to give a new aromatic compound. How to Make a Disposable Vape Last Longer? in here like that. (LogOut/ On a quick glance you might think that as 10 pi electrons are delocalized on 10 carbon atoms in case of naphthalene, it should have resonance energy per bond similar to that of benzene and thus making both equally active towards electrophiles. . In electrophilic aromatic substitution reactions, naphthalene reacts more readily than benzene. Three important contributing structures to the resonance hybrid may be drawn, as shown in the following diagram. To log in and use all the features of Khan Academy, please enable JavaScript in your browser. These catbon atoms bear no hydrogen atoms. Asking for help, clarification, or responding to other answers. As seen above, the electrons are delocalised over both the rings. Benzene, however, is an extraordinary 36 kcal/mole more stable than expected. b) Alkyl groups are activating and o,p-directing. However, you may visit "Cookie Settings" to provide a controlled consent. Naphthalene is a bicyclic aromatic hydrocarbon having a resonance stabilization energy per ring slightly less than that of benzene (36 kcal/mole). For example, rings can include oxygen, nitrogen, or sulfur. This difference, which is repeated for other equivalent ring bonds, is reflected in their bond lengths. Is it suspicious or odd to stand by the gate of a GA airport watching the planes? a five-membered ring. Naphthalene, on the other hand, is a neutral organic compound, and therefore is not soluble in water or the aqueous solutions that will be produced throughout the experiment. Examples for aromatic compounds are benzene, toluene etc. azure, as in blue. Naphthalene is a molecular compound. Benzene can form only one type of monosubstituted means that it cannot form different atoms just by replacing the position of attached atom like in ortho, para or meta position which occurs when two atoms are attached to it. And then these electrons right next to each other, which means they can overlap. And therefore each carbon has a Why benzene is more aromatic than naphthalene? @satyamkumarjha Yes you are right, naphthalene has higher nucleophilicity as well as higher electrophilicity than benzene. Naphthalene. It is normal to cold feet before wedding? What are 2 negative effects of using oil on the environment? a resonance structure for naphthalene, I could My attempt: Originally, benzene was considered aromatic because of its smell: it has an aromatic odor. Abstract. Why chlorobenzene is less reactive than benzene towards electrophilic substitution reaction? As discussed Both are aromatic in nature both have delocalised electrons but naphthalene has more resonance structures and more delocalisation so overall it must be more stable for a single ring. Why is naphthalene aromatic? Naphthalene has two aromatic rings, but only 10 pi electrons (rather than the twelve electrons that it would prefer). Naphthalene has two aromatic rings, but only 10 pi electrons (rather than the twelve electrons that it would prefer). Aromatic Hydrocarbons are especially stable, unsaturated cyclic compounds made primarily of hydrogen and carbon atoms. Note that all the carbon atoms except those at the points of fusion have a bond to a hydrogen atom. electrons are fully delocalized The chemical naphthalene is used to make the beta-blocking drug nadoxolol. out to be sp2 hybridized. Naphthalene It is the largest constituent of Coal tar It is obtained by cooling middle and Heavy oil The crude naphthalene is melted and treated with sulphuric aicid to remove basic impurities. of representing that resonance structure over here. stable as benzene. Note: Pi bonds are known as delocalized bonds. Again NIST comes to our rescue. ** Please give a detailed explanation for this answer. If a molecule contains an aromatic sub-unit, this is often called an aryl group. See Answer Question: Why naphthalene is less aromatic than benzene? What is \newluafunction? that this would give us two aromatic rings, Edit: As pointed out in the comments, I have made an error in counting the number of pi electrons in napthlene. Linear regulator thermal information missing in datasheet. This means that naphthalene has less aromatic stability than two isolated benzene rings would have. Acute (short- term) exposure of humans to naphthalene by inhalation, ingestion, and dermal contact is associated with hemolytic anemia, damage to the liver, and neurological damage. We also use third-party cookies that help us analyze and understand how you use this website. No, it's a vector quantity and dipole moment is always from Positive to Negative. These pages are provided to the IOCD to assist in capacity building in chemical education. Pi bonds cause the resonance. Naphthalene =unsaturated. Thus, resonance energy per ring for anthracene(3 rings) = 84 3 = 28kcal/mol. As an aromatic hydrocarbon, naphthalenes structure consists of a fused pair of benzene rings. overlapping p orbitals. This partial localization of pi electrons increases the nucleophilicity of naphthalene and thus makes it more active towards electrophiles than benzene. This means that naphthalene hasless aromatic stability than two isolated benzene rings would have. Technically , n aphthalene has fused rings unlike benzene and thus the two systems are different and cannot be compared. Chemical compounds containing such rings are also referred to as furans. It has a total of Direct link to Ernest Zinck's post Ordinary single and doubl, Posted 9 years ago. 1226 CHAPTER 25 THE CHEMISTRY OF THE AROMATIC HETEROCYCLES B. Acidity of Pyrrole and Indole Pyrrole and indole are weak acids. Naphthalene is the most abundant single constituent of coal tar, a volatile product from the destructive distillation of coal, and is also formed in modern processes for the high-temperature cracking (breaking up of large molecules) of petroleum. Moth balls containing naphthalene are generally safe for use around adults and older children, if used correctly and in the right quantity. These compounds show many properties linked with aromaticity. This cookie is set by GDPR Cookie Consent plugin. negative 1 formal charge. There are since pi-electrons in this benzene, these pi-electrons are delocalized throughout the whole molecule. The $\ce{C^1{}C^2}$ bond is $\pu{1.36 }$ long, whereas the $\ce{C^2{}C^3}$ bond length is So these, these, and Nitration at position 1 produces a carbocation that has 7 total resonance structures, 4 of which appear to preserve the aromaticity of the second ring. The cookie is used to store the user consent for the cookies in the category "Performance". How do/should administrators estimate the cost of producing an online introductory mathematics class? They are also called aromatics or arenes. And then this And so if I were to analyze 10 carbons in naphthalene. three resonance contributors, the carbon-carbon bonds in naphthalene Chemicals and Drugs 134. Why reactivity of NO2 benzene is slow in comparison to benzene? Naphthalene is more reactive than benzene. Nitration at position 2 produces a carbocation that has 6 total resonance structures, 2 of which appear to preserve the aromaticity of the second ring. Benzene shows that it is actually unsaturated because it adds hydrogen or chlorine, although only when allowed to react under very vigorous conditions (higher temperature or pressure) compared to those required for alkenes and alkynes. One structure has two identifiable benzene rings and the other two are 10 -electron annulenes. How to tell which packages are held back due to phased updates. What event was President Bush referring to What happened on that day >Apex. And so this is one Direct link to Erika Crowley's post Shouldn't the dipole face, Posted 7 years ago. Naphthalene is also planar and has 4n + 2 pi electrons (10) giving it the stabilizing and resonating aromatic properties shared with benzene. Stabilization energy = -143-(-80) = -63kcal/mol. Aromatic molecules are sometimes referred to simply as aromatics. Linear Algebra - Linear transformation question. Naphthalene is more reactive towards electrophilic substitution reactions than benzene. known household fumigant. the resonance energy for naphthalene is $61$ kcal/mol, The most recent value for the heat of hydrogenation from naphthalene to tetralin is $-125$ kJ/mol, $n$-th energy level for an electron confined in a single dimensional box, We've added a "Necessary cookies only" option to the cookie consent popup. And then these It is thus perfectly reasonable to rationalise that more delocalisation results in more stability. In the molten form it is very hot. In benzene 6 pi electrons are being shared between 6 carbons while in napthlene 12 pi electrons are being shared between 10 carbons so it is more electron dense. As both these energies are less than the resonance energy of benzene, benzene is more stable than anthracene and phenanthrene. Both are aromatic in nature both have delocalised electrons but naphthalene has more number of $\pi$ bonds and hence more resonance structures and more delocalisation so overall it must be more stable. Naphthalene, as a covalent compound, is made up of covalent molecules only. So I could draw If I look over Benzene has six pi electrons for its single aromatic ring. ring on the left. All the carbon atoms are sp2 hybridized. Aromatic rings are stable because they are cyclic, conjugated molecules. we have the dot structure for naphthalene. A long answer is given below. You can see that you have Where is H. pylori most commonly found in the world. electron density on the five-membered ring. 5)Naphthalene shows substitution reactions with electrophiles rather than addition reactions , just as benzene. And it's called azulene. Obviously, naphthalene is less stable and hence more reactive than benzene. The reason is that the most favorable resonance structures for either intermediate are those that have one fully aromatic ring. another example which is an isomer of naphthalene. How does nitration of naphthalene and anthracene preserve aromaticity? Therefore the order of resonance energy as per the benzene ring in the decreasing order is : Benzene > Naphthalene > Phenanthrene > Anthracene. Change), You are commenting using your Twitter account. But instead of electrons over here, move these electrons This molecule has 10 p-orbitals over which can overlap. You also have the option to opt-out of these cookies. Surfactants are made from the sulfonated form of naphthalene. So I could show those thank you. How is naphthalene aromatic? aromatic stability. I'm curious why the top carbon of the five-membered ring is sp2 hybridized rather than sp3; with the hydrogen attached, two C-C bonds, and the lone pair it seems like it should be sp3. Therefore, the naphthalene is an aromatic compound according to Huckel's rule because it has 4n+2 delocalised electrons. In terms of heat of hydrogenation Naphthalene can be hydrogenated to give tetralin . we can figure out why. aromatic hydrocarbon. aromatic stability. c) Ammonio groups are m-directing but amino groups are and o,p-directing. Naphthalene is the simplest polycyclic aromatic hydrocarbon since it is only a bicyclic molecule made up of two aromatic benzenes. Save my name, email, and website in this browser for the next time I comment. And then this ring The compound which would be more electron rich would also be more reactive to electrophilic aromatic substitution. MathJax reference. Thus naphthalene is less aromatic but more reactive . Naphthalene consists of two benzene rings that are fused together; the resulting molecule is still aromatic, and undergoes the reactions that are typical of benzene itself. p orbital, so an unhybridized p orbital. The tricyclic aromatic hydrocarbon phenanthrene has substantial resonance stabilization, as shown in the following diagram. From heats of hydrogenation or combustion, the resonance energy of Equation alignment in aligned environment not working properly, Euler: A baby on his lap, a cat on his back thats how he wrote his immortal works (origin?). . blue are right here. in the p orbitals on each one of my carbons So over here on the So let me go ahead . longer wavelength. Despite keen interest in the development of efficient materials for the removal of polycyclic aromatic hydrocarbons (PAHs) in wastewater, the application of advanced composite materials is still unexplored and needs attention. A covalent bond involves a pair of electrons being shared between atoms. Therefore, the naphthalene is an aromatic compound according to Huckel's rule because it has 4n+2 delocalised electrons . Based upon global structural searches and B3LYP and CCSD(T) calculations, we present herein the perfectly planar dicyclic boron And so it has a very As we are getting a whole number from, 4n+2 formula for naphthalene, so naphthalene is aromatic. Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers, and students in the field of chemistry. a) Acetyl and cyano substituents are both deactivating and m-directing. In the next post we will discuss some more PAHs. Anthracene is solid in state and consists of polycyclic aromatic hydrocarbon. Camphor and naphthalene unsaturated and alcohol is saturated. What materials do you need to make a dreamcatcher? It is the simplest polycyclic aromatic hydrocarbon, and is a white crystalline solid with a characteristic odor that is detectable at concentrations as low as 0.08 ppm by mass.