Amin (hemija) — разлика између измена
Садржај обрисан Садржај додат
. |
. |
||
Ред 1:
{| class="wikitable" style="margin:auto 1em auto 1em; float:right; text-align:center;"
|- id="amino_group_connectivity_table"
! Primarni amin || Sekundarni amin || Tercijarni amin
|-
| <center>[[Датотека:Primary-amine-2D-general.png|100px|primarni amin]]</center> || <center>[[Датотека:Secondary-amine-2D-general.png|100px|sekundarni amin]]</center> || <center>[[Датотека:Amine-2D-general.png|100px|tercijarni amin]]</center>
|}
'''Amini''' pripadaju grupi [[Organska jedinjenja|organskih jedinjenja]] koja sadrže najmanje jednu ili više baznih [[azot]]ovih atoma u molekulu. Amini se smatraju derivatima [[amonijak]]a i strukturno su mu sliči. Jedan ili više [[vodonik]]ovih atoma zamijenjen sa jednom ili više [[alkil]]nih ili [[aril]]nih organskih grupa.<ref>{{McMurry3rd}}</ref> Važni amini su [[aminokiselina|aminokiseline]], [[trimetilamin]]i, i [[anilin]]i. Neorganski derivati amonijaka se takođe nazivaju aminima, npr. hloramin (-{NClH}-<sub>2</sub>).
Slični aminima su [[amid]]i, međutim oni su derivati [[karboksilne kiseline|karboksilnih kiselina]] i imaju karbonilnu grupu vezanu na amino skupinu, npr.: -{RC(O)NR}-<sub>2</sub>. Amidi i amini imaju različitu strukturu i svojstva, stoga je razlika u nazivu važna. Supstituent --{NH}-<sub>2</sub> se naziva amino grupa.<ref name=OChemSmith3E>{{cite book |last1=Smith |first1=Janice Gorzynski |editor1-last=Hodge |editor1-first=Tami |editor2-last=Nemmers |editor2-first=Donna |editor3-last=Klein |editor3-first=Jayne |title=Organic chemistry |date=2011 |publisher=McGraw-Hill |location=New York, NY |isbn=978-0-07-337562-5 |pages=949-993 |edition=3rd |url=http://highered.mheducation.com/sites/007340277x/student_view0/index.html |language=en |format=Book |chapter=Chapter 25 Amines}}</ref> Jedinjenja sa atomom azota vezanim za [[karbonil]] grupu, koja imaju strukturu -{R–CO–NR′R″}-, se nazivaju [[amid]]ima i imaju različita hemijska svojstva od amina.<ref>Harrison L. G. (2011): The shaping of life: The generation of biological pattern. Cambridge University Press, ISBN 978-0-521-55350-6; http://books.google.com/books?id=-IPG-vg7Pr8C.</ref><ref>Hadžiselimović R., Pojskić N. (2005): Uvod u humanu imunogenetiku. Institut za genetičko inženjerstvo i biotehnologiju (INGEB), Sarajevo, ISBN 9958-9344-3-4.</ref><ref>Alberts B. (2002)ː Molecular biology of the cell. Garland Science, New York, ISBN 0-8153-3218-1.</ref><ref>Bajrović K, Jevrić-Čaušević A., Hadžiselimović R., Ed. (2005): Uvod u genetičko inženjerstvo i biotehnologiju. Institut za genetičko inženjerstvo i biotehnologiju (INGEB), Sarajevo, ISBN 9958-9344-1-8.</ref><ref>Kapur Pojskić L., Ed. (2014): Uvod u genetičko inženjerstvo i biotehnologiju, 2. izdanje. Institut za genetičko inženjerstvo i biotehnologiju (INGEB), Sarajevo, ISBN 978-9958-9344-8-3.</ref>
== Nomenklatura amina ==
* prefiks '''-{N}-''' označava supstituciju na atomu azota (npr.: -{N,N}--dimetiletilamin)
* kao prefiks: „amino-”"
* kao sufiks: „-amin”
Kod nižih amina koristi se sufiks -amin, a kod viših amina koristi se prefiks amino-.
* Primarni amini: [[metilamin]], [[etanolamin]] ili 2-aminoetanol
* Sekundarni amini: [[dimetilamin]], [[metiletanolamin]] ili 2-(metilamino)etanol
* Tercijarni amini: [[trimetilamin]], [[dimetiletanolamin]] ili 2-(dimetilamin)etanol
Četvrta podkategorija je određena povezanošću supstituenata vezanih za azot:
*'''Ciklični amini''' — [[Ciklično jedinjenje|Ciklični]] amini su bilo sekundarni ili tercijarni amini. Primeri cikličnih amina su tročlani prsten [[aziridin]]a i šestočlani prsten [[piperidin]]a. -{''N''}--metilpiperidin i -{''N''}--fenilpiperidin su primeri cikličnih tercijarnih amina.
Isto tako je moguće da postoje četiri organska supstituenta na azotu. Ove vrste nisu amini već su [[kvaternarni amonijum katjon]]i i imaju naelektrisani azotni centar. Kvaternarne amonijum soli postoje sa mnogim vrstama anjona.
== Fizička svojstva ==
[[Vodonična veza]] znatno utiče na svojstva amina<ref>{{RubberBible87th}}</ref>, zbog toga je tačka ključanja viša nego kod sličnih [[alkan]]a i niža od sličnih [[alkohol]]a. Zbog veće [[elektronegativnost]]i [[kiseonik]]a od azota, amini su više bazični od alkohola i alkana koji su time kiseliji. Amini manjih relativnih molekulskih masa (metil-, dimetil-, trimetil- i [[etilamin]]) su gasovi pri sobnoj temperaturi. Amini veće molekulske mase su tečnosti ili čvrste materije ([[dietilamin]] ili [[trietilamin]]).
Gasoviti amini imaju neugodan miris sličan [[amonijak]]u, dok tečni amini mirišu poput pokvarene ribe. Amini s manjim brojem ugljenikovih atoma dobro se rastvaraju u vodi stvarajući vodonične veze, rastvorljivost se smanjuje s povećanjem molekulske mase amina - odnosno hidrofobnog dela molekula. Alifatični amini dobro su rastvorni u organskim rastvaračima, pogotovo polarnim. Primarni amini reagiraju sa [[keton]]ima kao što je [[aceton]].
=== Spektroskopska identifikacija ===
Tipično se prisustvo aminske funkcionalne grupe određuje kombinacijom tehnika, uključujući masenu spektrometriju kao i NMR i IR spektroskopije. <sup>1</sup>-{H}- NMR signali za amini nestaju nakon tretiranja uzorka sa -{D}-<sub>2</sub>O. U svom [[infrared spectrum|infracrvenom spektru]] primarni amini ispoljavaju dve -{N-H}- veze, dok sekundarni amini imaju samo jednu.<ref name=OChemSmith3E />
== Struktura ==
{{rut}}
=== Alifatični amini ===
Razlikuju se tri vrste amina: '''primarni, sekundarni i tercijarni''', i to s obzirom na broj ugljovodoničnih grupa vezanih za azotov atom umjesto vodonika. Slovo '''-{R}-''' označava organsku (ugljovodoničnu) grupu.
Alkil amini karakteristično imaju tetrahedral nitrogen centers. C-N-C and C-N-H angles approach the idealized angle of 109°. C-N distances are slightly shorter than C-C distances. The energy barrier for the [[nitrogen inversion]] of the stereocenter is about 7 [[kcal/mol]] for a trialkylamine. The interconversion has been compared to the inversion of an open umbrella into a strong wind.
Amines of the type NHRR′ and NRR′R″ are [[chirality (chemistry)|chiral]]: the nitrogen center bears four substituents counting the lone pair. Because of the low barrier to inversion, amines of the type NHRR′ cannot be obtained in optical purity. For chiral tertiary amines, NRR′R″ can only be resolved when the R, R′, and R″ groups are constrained in cyclic structures such as N-substituted [[aziridine]]s ([[quaternary ammonium salt]]s are resolvable).
{| style="width:272px; float:right; margin-left:2em; margin-bottom:1ex;"
|[[File:Amine R-N.svg|76px]]
| style="font-size:200%" | ⇌
|[[File:Amine N-R.svg|76px]]
|-
| colspan=3 style="font-size:small" |Inversion of an amine. The pair of dots represents the lone electron pair on the nitrogen atom.
|}
=== Aromatični amini ===
Aromatični amini na azotovom atomu imaju vezan [[aromatični prsten]], trivijalno se zovu [[anilin]]i, primer je [[fenilamin]]. Anilin i njegovi derivati su u industrijskoj sintezi boja polazna jedinjenja. Aromatični prsten snižava bazičnost amina zavisno od supstituenata, a prisustvo amino grupe povećava reaktivnost kod aromatičnog prstena, zbog elektron-donatora. Jedna od reakcija aromatičnog prstena je [[Goldbergova reakcija]].
In aromatic amines ("anilines"), nitrogen is often nearly planar owing to conjugation of the lone pair with the aryl substituent. The C-N distance is correspondingly shorter. In aniline, the C-N distance is the same as the C-C distances.<ref>G. M. Wójcik "Structural Chemistry of Anilines" in Anilines (Patai's Chemistry of Functional Groups), S. Patai, Ed. 2007, Wiley-VCH, Weinheim. {{DOI|10.1002/9780470682531.pat0385}}</ref>
== Bazičnost ==
Like ammonia, amines are [[base (chemistry)|bases]].<ref>{{cite journal|title=Basicity and complex formation|journal= Patai's Chemistry of Functional Groups|editor=S. Patai|year=1968||author=J. W. Smith||doi=10.1002/9780470771082.ch4}}</ref> Compared to alkali metal hydroxides, amines are weaker (see table for examples of [[conjugate acid]] ''K''<sub>a</sub> values).
{| class="wikitable" style="float:center; margin:0 1em;"
|-
!Alkylamine<ref>{{Cite journal | last1 = Hall | first1 = H. K. | title = Correlation of the Base Strengths of Amines | doi = 10.1021/ja01577a030 | journal = Journal of the American Chemical Society | volume = 79 | issue = 20 | pages = 5441–5444 | year = 1957 | pmid = | pmc = }}</ref> or aniline<ref>{{Cite journal | last1 = Kaljurand | first1 = I. | last2 = Kütt | first2 = A. | last3 = Sooväli | first3 = L. | last4 = Rodima | first4 = T. | last5 = Mäemets | first5 = V. | last6 = Leito | first6 = I. | last7 = Koppel | first7 = I. A. | doi = 10.1021/jo048252w | title = Extension of the Self-Consistent Spectrophotometric Basicity Scale in Acetonitrile to a Full Span of 28 pKa Units: Unification of Different Basicity Scales | journal = The Journal of Organic Chemistry | volume = 70 | issue = 3 | pages = 1019–1028 | year = 2005 | pmid = 15675863| pmc = }}</ref>
! pK<sub>a</sub> of protonated amine
! ''K''<sub>b</sub>
|-
| [[methylamine]] (MeNH<sub>2</sub>)
| 10.62
| 4.17E-04
|-
| [[dimethylamine]] (Me<sub>2</sub>NH)
| 10.64
| 4.37E-04
|-
| [[trimethylamine]] (Me<sub>3</sub>N)
| 9.76
| 5.75E-05
|-
| [[ethylamine]] (EtNH<sub>2</sub>)
| 10.63
| 4.27E-04
|-
| [[aniline]] (PhNH<sub>2</sub>)
| 4.62
| 4.17E-10
|-
| [[p-Anisidine|4-methoxyaniline]] (4-MeOC<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>)
| 5.36
| 2.29E-09
|-
| [[N,N-Dimethylaniline]] (PhNMe<sub>2</sub>)
| 5.07
| 1.17E-09
|-
| [[3-Nitroaniline]] (3-NO<sub>2</sub>-C<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>)
| 2.46
| 2.88E-12
|-
| [[4-Nitroaniline]] (4-NO<sub>2</sub>-C<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>)
| 1
| 1.00E-13
|-
| 4-trifluoromethylaniline (CF<sub>3</sub>C<sub>6</sub>H<sub>4</sub>NH<sub>2</sub>)
| 2.75
| 5.62E-12
|}
The basicity of amines depends on:
# The electronic properties of the substituents (alkyl groups enhance the basicity, aryl groups diminish it).
# The degree of solvation of the protonated amine, which includes [[steric hindrance]] by the groups on nitrogen.
===Electronic effects===
Owing to inductive effects, the basicity of an amine might be expected to increase with the number of alkyl groups on the amine. Correlations are complicated owing to the effects of solvation which are opposite the trends for inductive effects. Solvation effects also dominate the basicity of aromatic amines (anilines). For anilines, the lone pair of electrons on nitrogen delocalises into the ring, resulting in decreased basicity. Substituents on the aromatic ring, and their positions relative to the amine group, also affect basicity as seen in the table.
===Solvation effects===
Solvation significantly affects the basicity of amines. N-H groups strongly interact with water, especially in ammonium ions. Consequently, the basicity of ammonia is enhanced by 10<sup>11</sup> by solvation. The intrinsic basicity of amines, i.e. the situation where solvation is unimportant, has been evaluated in the gas phase. In the gas phase, amines exhibit the basicities predicted from the electron-releasing effects of the organic substituents. Thus tertiary amines are more basic than secondary amines, which are more basic than primary amines, and finally ammonia is least basic. The order of pK<sub>b</sub>'s (basicities in water) does not follow this order. Similarly aniline is more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution.<ref>{{March6th}}</ref>
In aprotic polar solvents such as [[Dimethyl sulfoxide|DMSO]], [[Dimethylformamide|DMF]], and [[acetonitrile]] the energy of solvation is not as high as in protic polar solvents like water and methanol. For this reason, the basicity of amines in these aprotic solvents is almost solely governed by the electronic effects.
==
=== Alkilacija ===
The most industrially significant amines are prepared from ammonia by [[alkylation]] with alcohols:<ref name=Ullmann/>
: ROH + NH<sub>3</sub> → RNH<sub>2</sub> + H<sub>2</sub>O
Unlike the reaction of amines with alkyl halides, the industrial method is [[green chemistry|green]] insofar that the coproduct is water. The reaction of amines and ammonia with alkyl halides is used for synthesis in the laboratory:
: RX + 2 R′NH<sub>2</sub> → RR′NH + [RR′NH<sub>2</sub>]X
Such reactions, which are most useful for alkyl iodides and bromides, are rarely employed because the degree of alkylation is difficult to control.<ref name=Ullmann>{{Cite book|doi=10.1002/14356007.a02_001|chapter=Amines, Aliphatic|title=Ullmann's Encyclopedia of Industrial Chemistry|year=2000|last1=Eller|first1=Karsten|last2=Henkes|first2=Erhard|last3=Rossbacher|first3=Roland|last4=Höke|first4=Hartmut|isbn=3527306730}}</ref> Selectivity can be improved via the [[Delépine reaction]], although this is rarely employed on an industrial scale.
=== Reduktivne rute ===
Via the process of [[hydrogenation]], [[nitrile]]s are reduced to amines using hydrogen in the presence of a nickel catalyst. Reactions are sensitive to acidic or alkaline conditions, which can cause hydrolysis of the –CN group. LiAlH<sub>4</sub> is more commonly employed for the reduction of nitriles on the laboratory scale. Similarly, LiAlH<sub>4</sub> reduces [[amide]]s to amines. Many amines are produced from aldehydes and ketones via [[reductive amination]], which can either proceed catalytically or stoichiometrically.
[[Anilin]] (-{C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub>}-) and its derivatives are prepared by reduction of the nitroaromatics. In industry, hydrogen is the preferred reductant, whereas, in the laboratory, tin and iron are often employed.
== Neke vrste amina ==
Линија 53 ⟶ 140:
=== Alkaloidi ===
{{glavni|Alkaloidi}}
Alkaloidi su ''amini u prirodi'', posebno u biljnom svetu. U prirodi većinom nastaju iz aminokiselina. Znatan broj alkaloida je otrovan, gorkog ukusa s vrlo jakim farmakološkim učinkom. Primeri alkaloida: [[kofein]] (nalazi se u kafi, čaju, bezalkoholnim pićima, letalna doza kofeina je 10 grama), [[nikotin]] (nalazi se u lišću duhana, letalna doza nikotina je 500 miligrama (u krvotoku)), [[morfin]] (nalazi se u opijumu, osušenom soku iz maka).
=== Triptamini ===
{{glavni|Triptamin}}
'''[[Triptamin]]i''' su alkaloidni monoamini. Stvaraju se oko indolnog prstena. Odgovaraju aminokiselini [[triptofan]]. Neki deluju kao [[neurotransmiter]]i, a neki kao [[halucinogen]]i ([[psihoaktivne droge]], [[psihodelične droge]]). Primeri triptamina: [[serotonin]], [[melatonin]], [[dimetiltriptamin]], [[psilocin]]. Droge vrste triptamina se nalaze u porodici ([[TiHKAL]]).
=== Feniletilamini ===
{{glavni|Feniletilamin}}
'''[[Feniletilamin]]i''' su alkaloidni monoamini. Odgovaraju aminokiselini [[fenilalanin]]. Supstituisani feniletilamini su jedinjenja sa mnoštvom funkcija: [[neurotransmiteri]], [[hormoni]], [[Психостимуланс|stimulanti]], [[halucinogeni]], [[antidepresivi]]. Primeri feniletilamina: [[dopamin]], [[adrenalin]], [[noradrenalin]], [[amfetamin]], [[metamfetamin]], [[meskalin]], [[MDMA]], [[tiramin]], [[salbutamol]]. Druge vrste feniletilamina se nalaze u porodici (-{[[PiHKAL]]}-).
== Vidi još ==
Линија 98 ⟶ 157:
== Reference ==
{{reflist|
== Spoljašnje veze ==
{{Commons category-lat|Amine}}
* [http://www.organic-reaction.com/synthetic-protocols/functionals-groups/primary-amine/ Sinteza primarnih amina - Sintetički protokoli]
{{Funkcionalne grupe-lat}}
{{Authority control-lat}}
[[Категорија:Амини|*]]
| |||