|
|
| Line 1: |
Line 1: |
| {{distinguish|Alkane|Alkene}}
| | If you've ever tried to lose fat then we learn which low calorie diets could only receive we thus far. Eventually, the body can grow accustomed to the lower amount of calories plus a metabolism may slow down accordingly. That's whenever we reach a weight loss plateau plus it could appear because if regardless what you do, the weight won't come off. This really is a fantastic time to test a carb cycling plan for weight reduction. Carb cycling plans have been chosen by body builders and fitness models for several time today however, haven't caught on really immediately among the general public. It's a shame considering carb cycling for fat reduction functions very effectively! If you follow this type of plan, you'll really trick your body into burning fat, permitting we to reach a fat loss goals. Give it a try for quick fat reduction.<br><br>The fat burning zone, indeed, burns a greater PERCENTAGE of fat, relative to total calories burned. But the higher intensity cardio or athletic training zone burns more TOTAL calories for the same length of time. This means that calorie burn calculator the total amount of fat that's burned with these calories, actually comes out high than the total fat burned throughout simpler "fat burning" function.<br><br>As reported above, these people cannot procedure carbohydrates, and hence, the intake of carbohydrates should be reduced. This does not signify that they should not eat carbohydrates at all. They should avoid eating processed carbohydrates; and rather eat slow absorbing carbohydrates because they do not convert into fat. We must have complex carbohydrates like complete wheat treatments, whole wheat bread and pasta, brown rice, oatmeal, cereals, etc.<br><br>The just method to understand for sure how countless calories we burn doing insanity is to buy a heart rate monitor which furthermore tracks the amount of calories you burn. You are able to pick one of these up at a regional Wal Mart or fitness store for very cheap [http://safedietplansforwomen.com/calories-burned-walking calorie burn calculator]. A heart rate monitor, with the calorie count function included, may be strapped to the body while doing the Insanity workout. This will aid you to know for certain precisely where you fall in the range I reported earlier.<br><br>If you intensify the exercise, you are able to continuously burn fat. After you exercise your calories burned calculator metabolism speeds up. Thus, we should exercise each morning to optimize the effects of burning fats. Consult our important source regarding body fat calculator by clicking the link.<br><br>Eating frequently can keep a bodies' sugar degrees at the correct degrees, turning your body into a fat burning machine. You must eat 4-6 little very nutritional food a day however, a minimal of 3. While we eat frequently your body may expect the normal stamina and discover no have to shop fat for later so to not place the body into fat storing mode we need to provide it with the correct amount of foods at the correct times.<br><br>Changing the lifestyle to keep the pounds off is a bit hard, a long expression dedication, however, no question the benefits are real. Make healthy lifestyle options starting today! |
| | |
| [[File:Acetylene-3D-vdW.png|Alkyne|right|thumb|250px|A 3D model of ethyne ([[acetylene]]), the simplest alkyne]]
| |
| In [[organic chemistry]], an '''alkyne''' is an [[Saturation (chemistry)|unsaturated]] [[hydrocarbon]] which has at least one carbon—carbon [[triple bond]] between two [[carbon]] atoms.<ref>[http://www.britannica.com/EBchecked/topic/15818/alkyne Alkyne]. Encyclopædia Britannica</ref> The simplest acyclic alkynes with only one triple bond and no other [[functional group]]s form a [[homologous series]] with the general chemical formula {{Carbon}}<sub>n</sub>{{Hydrogen}}<sub>2n-2</sub>. Alkynes are traditionally known as acetylenes, although the name ''acetylene'' also refers specifically to C<sub>2</sub>H<sub>2</sub>, known formally as [[ethyne]] using [[IUPAC nomenclature of organic chemistry|IUPAC nomenclature]]. Like other hydrocarbons, alkynes are generally hydrophobic but tend to be more reactive.
| |
| | |
| ==Chemical properties==
| |
| Alkynes are characteristically more [[Saturation (chemistry)|unsaturated]] than alkenes. Thus they add two equivalents of [[bromine]] whereas an alkene adds only one equivalent. Other reactions are listed below. In some reactions, alkynes are less reactive than [[alkene]]s. For example, in a molecule with an -ene and an -yne group, addition occurs preferentially at the -ene.<ref>{{cite book|last=Rosser & Williams|title=Modern Organic Chemistry for A-level|year=1977|publisher=Collins|location=Great Britain|isbn=0003277402|page=82}}</ref> Possible explanations involve the two π-bonds in the alkyne delocalising, which would reduce the energy of the π-system{{citation needed|date=June 2013}} or the stability of the intermediates during the reaction.
| |
| They show greater tendency to [[Polymerization|polymerize]] or [[oligomer]]ize than alkenes do. The resulting polymers, called [[polyacetylene]]s (which do not contain alkyne units) are [[conjugated system|conjugated]] and can exhibit semiconducting properties.
| |
| | |
| ==Structure and bonding==
| |
| In acetylene, the H–C≡C [[bond angle]]s are 180°. By virtue of this bond angle, alkynes tend to be rod-like. Correspondingly, cyclic alkynes are rare. [[Benzyne]] is highly unstable. The C≡C bond distance of 121 [[picometer]]s is much shorter than the C=C distance in [[alkene]]s (134 pm) or the C-C bond in alkanes (153 pm).
| |
| | |
| :[[File:Alkyne General Formulae V.2.png|thumb|center|580px|Illustrative alkynes: '''a''', acetylene, '''b''', two depictions of propyne, '''c''', 1-butyne, '''d''', 2-butyne, '''e''', the naturally-occurring 1-phenylhepta-1,3,5-triyne, and '''f''', the strained cycloheptyne. Triple bonds are highlighted <span style="color:blue;">'''blue'''</span>.]]
| |
| | |
| The [[triple bond]] is very strong with a [[bond strength]] of 839 kJ/mol. The sigma bond contributes 369 kJ/mol, the first pi bond contributes 268 kJ/mol and the second pi-bond of 202 kJ/mol bond strength. Bonding usually discussed in the context of [[molecular orbital theory]], which recognizes the triple bond as arising from overlap of s and p orbitals. In the language of [[valence bond theory]], the carbon atoms in an alkyne bond are [[sp hybridized]]: they each have two unhybridized [[p orbital]]s and two [[Orbital hybridisation|sp hybrid orbitals]]. Overlap of an sp orbital from each atom forms one sp-sp [[sigma bond]]. Each p orbital on one atom overlaps one on the other atom, forming two [[pi bond]]s, giving a total of three bonds. The remaining sp orbital on each atom can form a sigma bond to another atom, for example to hydrogen atoms in the parent acetylene. The two sp orbitals project on opposite sides of the carbon atom.
| |
| | |
| ===Terminal and internal alkynes===
| |
| Internal alkynes feature carbon substituents on each acetylenic carbon. Symmetrical examples include [[diphenylacetylene]] and [[3-hexyne]].
| |
| | |
| Terminal alkynes have the formula RC<sub>2</sub>H. An example is [[methylacetylene]] (propyne using IUPAC nomenclature). Terminal alkynes, like [[acetylene]] itself, are mildly acidic, with p''K''<sub>a</sub> values of around 25. They are far more acidic than alkenes and alkanes, which have p''K''<sub>a</sub> values of around 40 and 50, respectively. The acidic hydrogen on terminal alkynes can be replaced by a variety of groups resulting in halo-, silyl-, and alkoxoalkynes. The carbanions generated by deprotonation of terminal alkynes are called [[acetylide]]s.<ref name="de57">{{cite book|last=Bloch|first=Daniel R.|title=Organic Chemistry Demystified|year=2012|publisher=McGraw-Hill|isbn=978-0-07-176797-2|pages=57|edition=2|accessdate=26 July 2012}}</ref>
| |
| | |
| ==Synthesis==
| |
| Commercially, the dominant alkyne is acetylene itself, which is used as a fuel and a precursor to other compounds, e.g., acrylates. Hundreds of millions of kilograms are produced annually by partial oxidation of [[natural gas]]:<ref name=Ullmann/>
| |
| : 2 CH<sub>4</sub> + 3/2 O<sub>2</sub> → HC≡CH + 3 H<sub>2</sub>O
| |
| Propyne, also industrially useful, is also prepared by [[thermal cracking]] of hydrocarbons. Most other industrially useful alkyne derivatives are prepared from acetylene, e.g. via condensation with formaldehyde.<ref name=Ullmann>{{cite book |author=Peter Pässler, Werner Hefner, Klaus Buckl, Helmut Meinass, Andreas Meiswinkel, Hans-Jürgen Wernicke, Günter Ebersberg, Richard Müller, Jürgen Bässler, Hartmut Behringer, Dieter Mayer |chapter=Acetylene |title=Ullmann's Encyclopedia of Industrial Chemistry |publisher=Wiley-VCH |location=Weinheim |date=October 15, 2008 |isbn= |pages= |doi=10.1002/14356007.a01_097.pub3 }}</ref>
| |
| | |
| Specialty alkynes are prepared by [[dehydrohalogenation]] of [[Vicinal (chemistry)|vicinal]] alkyl [[Halide|dihalides]] or vinyl halides.<ref>{{OrgSynth | prep = cv4p0763 | collvol = 4 | collvolpages = 763 | year = 1963 | title = Phenylacetylene | author = Kenneth N. Campbell and Barbara K. Campbell}}</ref> Metal acetylides can be coupled with primary [[alkyl halide]]s. Via the [[Fritsch-Buttenberg-Wiechell rearrangement]], alkynes are prepared from [[vinyl bromide]]s. Alkynes can be prepared from [[aldehyde]]s using the [[Corey-Fuchs reaction]] and from aldehydes or [[ketone]]s by the [[Seyferth–Gilbert homologation]]. In the [[alkyne zipper reaction]], alkynes are generated from other alkynes by treatment with a strong base.
| |
| | |
| ==Reactions==
| |
| Featuring a reactive [[functional group]], alkynes participate in many [[organic reaction]]s.
| |
| | |
| ===Addition of hydrogen, halogens, and related reagents===
| |
| Alkynes characteristically undergo reactions that show that they are "doubly unsaturated", meaning that each alkyne unit is capable of adding two equivalents of H<sub>2</sub>, [[halogen]]s or related HX reagents (X = halide, pseudohalide, etc.). Depending on catalysts and conditions, alkynes add one or two equivalents of hydrogen. [[Hydrogenation]] to the [[alkene]] is usually more desirable since alkanes are less useful:
| |
| :RC≡CR' + H<sub>2</sub> → ''cis''-RCH=CR'H
| |
| The largest scale application of this technology is the conversion of acetylene to ethylene in refineries. The steam cracking of alkanes affords a few percent acetylene, which is selectively hydrogenated in the presence of a [[palladium]]/[[silver]] catalyst. For more complex alkynes, the [[Lindlar catalyst]] is widely recommended to avoid formation of the alkane, for example in the conversion of [[phenylacetylene]] to [[styrene]].<ref>{{OrgSynth | collvol = 5 | collvolpages = 880 | year = 1973 | prep = cv5p0880 | author = H. Lindlar and R. Dubuis | title = Palladium catalyst for partial reduction of acetylenes}}.</ref> | |
| | |
| :[[File:ApplicationLindlarCatalyst.svg|400px|center|Application Lindlar Catalyst]] | |
| | |
| Similarly, [[halogenation]] of alkynes gives the vinyl dihalides or alkyl tetrahalides:
| |
| | |
| :RC≡CR' + 2 Br<sub>2</sub> → RCBr<sub>2</sub>CRBr<sub>2</sub>
| |
| | |
| The addition of nonpolar E-H bonds across C≡C is general for silanes, boranes, and related hydrides. The [[hydroboration-oxidation reaction|hydroboration]] of alkynes gives vinylic boranes which oxidize to the corresponding [[aldehyde]] or ketone. In the [[thiol-yne reaction]] the substrate is a thiol.
| |
| | |
| [[Hydrohalogenation]] gives the corresponding [[vinyl halide]]s or alkyl dihalides, again depending on the number of equivalents of HX added. The addition of water to alkynes is a related reaction except the initial [[enol]] intermediate converts to the ketone or aldehyde. Illustrative is the hydration of [[phenylacetylene]] gives [[acetophenone]],<ref>{{cite journal | author = Fukuda, Y.; Utimoto, K. | title = Effective transformation of unactivated alkynes into ketones or acetals with a gold(III) catalyst | journal = [[J. Org. Chem.]] | doi = 10.1021/jo00011a058 | year = 1991 | volume = 56 | pages = 3729 | issue = 11}}.</ref> and the (Ph<sub>3</sub>P)AuCH<sub>3</sub>-catalyzed hydration of 1,8-nonadiyne to 2,8-nonanedione:<ref>{{OrgSynth | author = Mizushima, E.; Cui, D.-M.; Nath, D. C. D.; Hayashi, T.; Tanaka, M. | title = Au(I)-Catalyzed hydratation of alkynes: 2,8-nonanedione | volume = 83 | pages = 55 | year = 2005 | prep = v83p0055}}</ref>
| |
| :PhC≡CH + H<sub>2</sub>O → PhCOCH<sub>3</sub>
| |
| : HC≡CC<sub>6</sub>H<sub>12</sub>C≡CH + 2H<sub>2</sub>O → CH<sub>3</sub>COC<sub>6</sub>H<sub>12</sub>COCH<sub>3</sub>
| |
| | |
| ===Cycloadditions and oxidation===
| |
| Alkynes undergo diverse [[cycloaddition]] reactions. Most notable is the [[Diels–Alder reaction]] with 1,3-[[diene]]s to give [[1,4-cyclohexadienes]]. This general reaction has been extensively developed and electrophilic alkynes are especially effective [[dienophile]]s. The "cycloadduct" derived from the addition of alkynes to [[2-pyrone]] eliminates [[carbon dioxide]] to give the [[aromatic]] compound. Other specialized cycloadditions include multicomponent reactions such as [[alkyne trimerisation]] to give [[aromatic]] compounds and the [2+2+1]cycloaddition of an alkyne, [[alkene]] and [[carbon monoxide]] in the [[Pauson–Khand reaction]]. Non-carbon reagents also undergo cyclization, e.g. [[Azide alkyne Huisgen cycloaddition]] to give [[triazole]]s. Cycloaddition processes involving alkynes are often catalyzed by metals, e.g. [[enyne metathesis]] and [[alkyne metathesis]], which allows the scrambling of carbyne (RC) centers:
| |
| :RC≡CR + R'C≡CR' <math>\overrightarrow{\leftarrow}</math> 2 RC≡CR'
| |
| Oxidative cleavage of alkynes proceeds via cycloaddition to metal oxides. Most famously, [[potassium permanganate]] converts alkynes to a pair of [[carboxylic acid]]s.
| |
| | |
| ===Reactions specific for terminal alkynes===
| |
| In addition to undergoing the reactions characteristic of internal alkynes, terminal alkynes are reactive as weak acids, with [[Acid dissociation constant|pK<sub>a</sub>]] values (25) between that of [[ammonia]] (35) and [[ethanol]] (16). The acetylide [[conjugate base]] is stabilized as a result of the high s character of the sp orbital, in which the electron pair resides. [[Electron]]s in an s orbital benefit from closer proximity to the positively charged atom nucleus, and are therefore lower in energy. Treatment of terminal alkynes with a [[strong base]] gives the corresponding [[metal acetylide]]s:
| |
| :RC≡CH + MX → RC≡CM + HX (MX = [[sodium amide|NaNH<sub>2</sub>]], [[N-Butyllithium|LiBu]], [[Grignard reagent|RMgX]])
| |
| The reactions of alkynes with certain metal cations, e.g. Ag<sup>+</sup> also gives acetylides. Thus, few drops of [[Tollens reagent|diamminesilver(I) hydroxide]] (Ag(NH<sub>3</sub>)<sub>2</sub>OH) reacts with terminal alkynes signaled by formation of a white precipitate of the silver acetylide.
| |
| Acetylide derivatives are synthetically useful [[nucleophile]]s that participate in C-C bond forming reactions, as illustrated in the area called [[Carbonylation|"Reppe Chemistry"]].
| |
| | |
| In the [[Favorskii reaction]], terminal alkynes add to [[carbonyl]] compounds to give the [[hydroxyalkyne]]. [[Coupling reaction|Coupling]] of terminal alkynes to give di-alkynes is effected in the [[Cadiot-Chodkiewicz coupling]], [[Glaser coupling]], and the [[Eglinton coupling]] reactions. Terminal alkynes can also be coupled to aryl or vinyl halides as in the [[Sonogashira coupling]].
| |
| | |
| ==Alkynes in nature and medicine==
| |
| According to Ferdinand Bohlmann, the first naturally occurring acetylenic compound, dehydromatricaria ester, was isolated from an ''Artemisia'' species in 1826. In the nearly two centuries that have followed, well over a thousand naturally occurring acetylenes have been discovered and reported. Polyynes, a subset of this class of natural products, have been isolated from a wide variety of plant species, cultures of higher fungi, bacteria, marine sponges, and corals.<ref>{{cite journal | author = Annabelle L. K. Shi Shun; Rik R. Tykwinski| title = Synthesis of Naturally Occurring Polyynes| journal = Angew. Chem. Int. Ed. | year = 2006| volume = 45 | pages = 1034–1057| doi = 10.1002/anie.200502071 | issue = 7 | pmid=16447152}}</ref> Some acids like [[tariric acid]] contains an alkyne group. Diynes and triynes, species with the linkage RC≡C-C≡CR' and RC≡C-C≡C-C≡CR' respectively, occur in certain plants (''[[Ichthyothere]]'', ''[[Chrysanthemum]]'', ''[[Cicuta]]'', ''[[Water dropwort|Oenanthe]]'' and other members of the [[Asteraceae]] and [[Apiaceae]] families). Some examples are [[cicutoxin]], [[oenanthotoxin]], [[falcarinol]] and [[carotatoxin]]. These compounds are highly bioactive, e.g. as [[nematocide]]s.<ref>{{cite book |author=Lam, Jørgen |title=Chemistry and biology of naturally-occurring acetylenes and related compounds (NOARC): proceedings of a Conference on the Chemistry and Biology of Naturally-Occurring Acetylenes and Related Compounds (NOARC) |publisher=Elsevier |location=Amsterdam |year=1988 |pages= |isbn=0-444-87115-2 }}</ref> 1-Phenylhepta-1,3,5-triyne is illustrative of a naturally occurring triyne.
| |
| | |
| Alkynes occur in some pharmaceuticals, including the contraceptive [[norethynodrel]]. A carbon–carbon triple bond is also present in marketed drugs such as the antiretroviral [[Efavirenz]] and the antifungal [[Terbinafine]]. Molecules called ene-diynes feature a ring containing an alkene ("ene") between two alkyne groups ("diyne"). These compounds, e.g. [[calicheamicin]], are some of the most aggressive antitumor drugs known, so much so that the ene-diyne subunit is sometimes referred to as a "warhead." Ene-diynes undergo rearrangement via the [[Bergman cyclization]], generating highly reactive radical intermediates that attack DNA within the tumor.<ref>{{cite journal | author = S. Walker; R. Landovitz; W.D. Ding; G.A. Ellestad; D. Kahne | title = Cleavage behavior of calicheamicin gamma 1 and calicheamicin T | journal = Proc Natl Acad Sci U.S.A. | year = 1992| volume = 89 | issue = 10 | pages = 4608–12 | pmc=49132 | doi = 10.1073/pnas.89.10.4608 | pmid = 1584797|bibcode = 1992PNAS...89.4608W }}</ref>
| |
| | |
| ==See also==
| |
| {{wiktionary}}
| |
| * [[-yne]]
| |
| * [[cycloalkyne]]
| |
| | |
| ==References==
| |
| {{Reflist}}
| |
| | |
| {{Hydrocarbons}}
| |
| {{Alkynes}}
| |
| {{Functional Groups}}
| |
| {{BranchesofChemistry}}
| |
| | |
| [[Category:Alkynes| ]]
| |
| [[Category:Functional groups]]
| |
| | |
| {{Link GA|ru}}
| |
If you've ever tried to lose fat then we learn which low calorie diets could only receive we thus far. Eventually, the body can grow accustomed to the lower amount of calories plus a metabolism may slow down accordingly. That's whenever we reach a weight loss plateau plus it could appear because if regardless what you do, the weight won't come off. This really is a fantastic time to test a carb cycling plan for weight reduction. Carb cycling plans have been chosen by body builders and fitness models for several time today however, haven't caught on really immediately among the general public. It's a shame considering carb cycling for fat reduction functions very effectively! If you follow this type of plan, you'll really trick your body into burning fat, permitting we to reach a fat loss goals. Give it a try for quick fat reduction.
The fat burning zone, indeed, burns a greater PERCENTAGE of fat, relative to total calories burned. But the higher intensity cardio or athletic training zone burns more TOTAL calories for the same length of time. This means that calorie burn calculator the total amount of fat that's burned with these calories, actually comes out high than the total fat burned throughout simpler "fat burning" function.
As reported above, these people cannot procedure carbohydrates, and hence, the intake of carbohydrates should be reduced. This does not signify that they should not eat carbohydrates at all. They should avoid eating processed carbohydrates; and rather eat slow absorbing carbohydrates because they do not convert into fat. We must have complex carbohydrates like complete wheat treatments, whole wheat bread and pasta, brown rice, oatmeal, cereals, etc.
The just method to understand for sure how countless calories we burn doing insanity is to buy a heart rate monitor which furthermore tracks the amount of calories you burn. You are able to pick one of these up at a regional Wal Mart or fitness store for very cheap calorie burn calculator. A heart rate monitor, with the calorie count function included, may be strapped to the body while doing the Insanity workout. This will aid you to know for certain precisely where you fall in the range I reported earlier.
If you intensify the exercise, you are able to continuously burn fat. After you exercise your calories burned calculator metabolism speeds up. Thus, we should exercise each morning to optimize the effects of burning fats. Consult our important source regarding body fat calculator by clicking the link.
Eating frequently can keep a bodies' sugar degrees at the correct degrees, turning your body into a fat burning machine. You must eat 4-6 little very nutritional food a day however, a minimal of 3. While we eat frequently your body may expect the normal stamina and discover no have to shop fat for later so to not place the body into fat storing mode we need to provide it with the correct amount of foods at the correct times.
Changing the lifestyle to keep the pounds off is a bit hard, a long expression dedication, however, no question the benefits are real. Make healthy lifestyle options starting today!