Chemistry

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Aufbau Principle

Aufbau principle

The Aufbau principle (from the German Aufbau, "building up, construction") was an important part of Bohr's original concept of electron configuration. It may be stated as:[9]
a maximum of two electrons are put into orbitals in the order of increasing orbital energy: the lowest-energy orbitals are filled before electrons are placed in higher-energy orbitals.
The approximate order of filling of atomic orbitals, following the arrows.
 
The principle works very well (for the ground states of the atoms) for the first 18 elements, then increasingly less well for the following 100 elements. The modern form of the Aufbau principle describes an order of orbital energies given by Madelung's rule, first stated by Erwin Madelung in 1936.[8][10]
  1. Orbitals are filled in the order of increasing n+l;
  2. Where two orbitals have the same value of n+l, they are filled in order of increasing n.
This gives the following order for filling the orbitals:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, and 7p
The Aufbau principle can be applied, in a modified form, to the protons and neutrons in the atomic nucleus, as in the shell model of nuclear physics.



Energy Level                         (n+l)Value

1s                                                1
2s                                                2
2p 3s                                           3                      
3p 4s                                           4
3d 4p 5s                                      5
4d 5p 6s                                      6
4f 5d 6p 7s                                  7
5f 6d 7p 8s                                  8

Hint:
Energy level                     Order of filling
1&2                                     s
3&4                                   ps
5&6                                 dps
7&8                                fdps

Periodicity

This is a graph of ionization energy versus element atomic number.
This graph displays the periodic trend of ionization energy versus atomic number.
RJHall, Wikipedia Commons
The properties of the elements exhibit trends. These trends can be predicted using the periodic table and can be explained and understood by analyzing the electron configurations of the elements. Elements tend to gain or lose valence electrons to achieve stable octet formation. Stable octets are seen in the inert gases, or noble gases, of Group VIII of the periodic table. In addition to this activity, there are two other important trends. First, electrons are added one at a time moving from left to right across a period. As this happens, the electrons of the outermost shell experience increasingly strong nuclear attraction, so the electrons become closer to the nucleus and more tightly bound to it. Second, moving down a column in the periodic table, the outermost electrons become less tightly bound to the nucleus. This happens because the number of filled principal energy levels (which shield the outermost electrons from attraction to the nucleus) increases downward within each group. These trends explain the periodicity observed in the elemental properties of atomic radius, ionization energy, electron affinity, and electronegativity
 
Atomic Radius
The atomic radius of an element is half of the distance between the centers of two atoms of that element that are just touching each other. Generally, the atomic radius decreases across a period from left to right and increases down a given group. The atoms with the largest atomic radii are located in Group I and at the bottom of groups.
Moving from left to right across a period, electrons are added one at a time to the outer energy shell. Electrons within a shell cannot shield each other from the attraction to protons. Since the number of protons is also increasing, the effective nuclear charge increases across a period. This causes the atomic radius to decrease.
Moving down a group in the periodic table, the number of electrons and filled electron shells increases, but the number of valence electrons remains the same. The outermost electrons in a group are exposed to the same effective nuclear charge, but electrons are found farther from the nucleus as the number of filled energy shells increases. Therefore, the atomic radii increase.
 
Ionization Energy
The ionization energy, or ionization potential, is the energy required to completely remove an electron from a gaseous atom or ion. The closer and more tightly bound an electron is to the nucleus, the more difficult it will be to remove, and the higher its ionization energy will be. The first ionization energy is the energy required to remove one electron from the parent atom. The second ionization energy is the energy required to remove a second valence electron from the univalent ion to form the divalent ion, and so on. Successive ionization energies increase. The second ionization energy is always greater than the first ionization energy. Ionization energies increase moving from left to right across a period (decreasing atomic radius). Ionization energy decreases moving down a group (increasing atomic radius). Group I elements have low ionization energies because the loss of an electron forms a stable octet.
 
Electron Affinity
Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electron is added to a gaseous atom. Atoms with stronger effective nuclear charge have greater electron affinity. Some generalizations can be made about the electron affinities of certain groups in the periodic table. The Group IIA elements, the alkaline earths, have low electron affinity values. These elements are relatively stable because they have filled s subshells. Group VIIA elements, the halogens, have high electron affinities because the addition of an electron to an atom results in a completely filled shell. Group VIII elements, noble gases, have electron affinities near zero, since each atom possesses a stable octet and will not accept an electron readily. Elements of other groups have low electron affinities.
 
Electronegativity
Electronegativity is a measure of the attraction of an atom for the electrons in a chemical bond. The higher the electronegativity of an atom, the greater its attraction for bonding electrons. Electronegativity is related to ionization energy. Electrons with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons. Elements with high ionization energies have high electronegativities due to the strong pull exerted on electrons by the nucleus. In a group, the electronegativity decreases as atomic number increases, as a result of increased distance between the valence electron and nucleus (greater atomic radius). An example of an electropositive (i.e., low electronegativity) element is cesium; an example of a highly electronegative element is fluorine.
 
Summary of Periodic Table Trends
Moving Left --> Right
  • Atomic Radius Decreases
  • Ionization Energy Increases
  • Electronegativity Increases
Moving Top --> Bottom
  • Atomic Radius Increases
  • Ionization Energy Decreases
  • Electronegativity Decreases

Chemical Abbreviations

1,1-DCE: 1,1-dichloroethylene (vinylidene chloride)
2-AAF: 2-acetamidofluorene
2-AB: sec-butylamine
2-CBA: 2-chlorobenzoic acid
2-CNB: 1-chloro-2-nitrobenzene
2-FAA: 2-acetamidofluorene
2-MBT: 2-mercaptobenzothiazole
2-ME: 2-mercaptoethanol
2,4-D: 2,4-dichlorophenoxyacetic acid
2,4-DNBF 2,4-dinitrofluorobenzene
2,4-DNP: 2,4-dinitrophenol
2,4-DNPH: 2,4-dinitrophenylhydrazine
2,4,5-T: 2,4,5-trichlorophenoxyacetic acid or 2,4,5-trichlorophenol
2,6-DCP 2,6-dichlorophenol
2,6-TDI: Toluene-2,6-diisocyanate
3-EP: 3-ethylpyridine
3-MC: 3-methylcholanthrene
3-MCA: 3-methylcholanthrene
3-PBA: 3-phenoxybenzyl alcohol
3-MECA: 3-methylcholanthrene
3,4-BP: Benzo(a)pyrene
3,4-DCP: 3,4-dichlorophenol
4,4'-DDT: Dichlorodiphenyltrichloroethane
4,4'-DADPE: 4,4'-oxydianiline
4M2AP: 2-amino-4-picoline
4-NDB: 4-nitro-o-phenylenediamine
4-NOP: 4-nitro-o-phenylenediamine
4-NOPD: 4-nitro-o-phenylenediamine
4-NQO: 4-nitroquinoline-N-oxide
4-PPP: 4-(3-phenylpropyl)pyridine
4-PPPy: 4-(3-phenylpropyl)pyridine
5-ASA: 5-aminosalicylic acid
5-BDU: 5-bromo-2'-deoxyuridine
5-FU: 5-fluorouracil
5-FUDR: 5-fluorodeoxyuridine
7-ADCA: 7-amino-3-methyl-3-cephem-4-carboxylic acid
8-OQ: 8-hydroxyquinoline
9-AA: 9-acridinamine
20-MC: 3-methylcholanthrene

    ***

AA: Ascorbic acid

    ***

AAF: 2-acetamidofluorene
AAN: Acetoacetanilide
AEP: Aminoethylpiperazine
AGE: Allyl glycidyl ether
AKD: Alkyl ketene dimer
AMP: 2-amino-2-methyl-1-propanol

    ***

AIBN: 2,2'-azobis(2-methylpropionitrile)
APCD: Ammonium 1-pyrrolidinecarbodithioate

    ***

BN: Boron nitride
BP: Benzo(a)pyrene

    ***

BAC: N,N'-bis(acrylyl)cystamine
BAL: 2,3-dimercapto-1-propanol
BCG: Bromocresol green
BCS: N-(benzyloxycarbonyloxy)succinimide
BDU: 5-bromo-2'-deoxyuridine
BHA: Butylated hydroxyanisole
BHT: Butylated hydroxytoluene
BKF: Benzo[k]fluoranthene
BNP: 3-nitropropionic acid
BNS: Beta-nitrostyrene
BOA: Butylated hydroxyanisole
BPA: Bisphenol A
BTM: Benzyltrimethylammonium chloride
BTZ: Phenylbutazone
BZI: Benzimidazole
BZT: Benzenthonium chloride

    ***

BBCE: 3,3'-iminodipropionitrile
BDMA: N,N-dimethylbenzylamine
BUDR: 5-bromo-2'-deoxyuridine

    ***

BAC-TE: Triethylbenzylammonium chloride
BCDMH: Bromochlorodimethylhydantoin
BRUDR: 5-bromo-2'-deoxyuridine

    ***

beta-HPN: Ethylene cyanohydrin

    ***

CG: Phosgene
CN: 2-chloroacetophenone
CS: o-chlorobenzylidene malononitrile

    ***

CAF: 2-chloroacetophenone
CAP: 2-chloroacetophenone
CCC: (2-chloroethyl)trimethylammonium chloride
CDA: Cetyldimethylethylammonium bromide
CNB: 2-chloroacetophenone
CNC: Copper naphthenate or 2-chloroacetophenone

    ***

CACP: Cisplatin
CAPS: 3-(cyclohexylamino)-1-propanesulfonic acid
CDDP: Cisplatin
CDNB: 1-chloro-2,4-dinitrobenzene
CPCA: Dicofol
CPDC: Cisplatin
CPDD: Cisplatin
CTAB: Hexadecyltrimethylammonium bromide

    ***

CBDCA: Carboplatin

    ***

DS: Diethyl sulfate

    ***

DAS: 4,4'-diamino-2,2'-stilbenedisulfonic acid
DBP: Dibutyl phthalate
DCA: Dichloroacetic acid
DCB: 1,2-dichlorobenzene
DCC: N,N'-dicyclohexylcarbodiimide
DCM: Dichloromethane or
[2-[2-[4-(dimethylamino)phenyl]ethenyl]-6-methyl-4H-pyran-4-ylidene]-propanedinitrile
DCS: 2-phenylphenol sodium salt tetrahydrate
DDC: Sodium diethyldithiocarbamate trihydrate
DDI: Dideoxyinosine
DDM: 4,4'-methylenedianiline
DDP: Cisplatin
DDS: 2-dodecen-1-ylsuccinic anhydride
DDT: Dichlorodiphenyltrichloroethane
DEA: N,N-diethylaniline
DEC: Diethyl carbonate
DEK: 3-pentanone
DEN: Diethylamine
DEP: Trichlorofon
DET: N,N-diethyl-N-toluamide
DFP: Diisopropylfluorophosphate
DMA: Dimethyl acetamide
DMF: Dimethylformamide
DMN: N-nitrosodimethylamine
DMP: Dimethyl phthalate
DMT: Dimethyl terephthalate
DMU: Diuron
DNA: 2,4-dinitroaniline
DOA: Bis(2-ethylhexyl) adipate
DOS: Dioctyl sebacate
DPA: 9,10-diphenylanthracene
DPD: N,N-diethyl-1,4-phenylenediamine
DPG: Diphenylguanidine
DSP: Sodium phosphate dibasic
DTE: Dithioerythritol

    ***

DADT: N,N'-diallyltartardiamide
DAPM: 4,4'-methylenedianiline
DASD: 4,4'-diamino-2,2'-stilbenedisulfonic acid
DBCP: 1,2-dibromo-3-chloropropane
DCAA: Dichloroacetic acid
DCDD: 2,7-dichlorodibenzo-p-dioxin
DCDP: Cisplatin
DCEE: 2-chloroethyl ether
DCMC: Diuron
DCMU: Diuron
DCNB: 3,4-dichloronitrobenzene
DDPt: Cisplatin
DEAE: Diethylaminoethanol
DEDC: Sodium diethyldithiocarbamate trihydrate
DEDK: Sodium diethyldithiocarbamate trihydrate
DEHA: Bis(2-ethylhexyl) adipate
DEHP: Dioctyl phthalate
DETA: N,N-diethyl-N-toluamide
DHES: Dioctyl sebacate
DITP: 2'-deoxyinosine-5'-triphosphate
DMAB: Borane-dimethylamine complex
DMAC: Dimethyl acetamide
DMDS: Methyl disulphide
DMFA: Dimethylformamide
DMHP: Dimethyl phosphite
DMNA: N-nitrosodimethylamine
DMMP: Dimethyl methylphosphonate
DMPO: 5,5-dimethyl-1-pyrroline N-oxide
DMPT: 1-phenyl-3,3-dimethyltriazine
DMSA: Succinic acid 2,2-dimethylhydrazide
DMSO: Dimethyl sulfoxide
DNCB: 1-chloro-2,4-dinitrobenzene
DNFB 2,4-dinitrofluorobenzene
DNPF 2,4-dinitrofluorobenzene
DPPA: Diphenylphosphoryl azide
DPPE: 1,2-bis(diphenylphosphino)ethane
DTBP: Di-t-butyl peroxide
DTMC: Dicofol
DTNB: 5,5'-dithiobis(2-nitrobenzoic_acid)
DTPA: Pentetic acid

    ***

DABCO: 1,4-diazabicyclo(2.2.2)octane
DACPM: 4,4'-methylenebis(2-chloroaniline)
DADPE: 4,4'-oxydianiline
DADPM: 4,4'-methylenedianiline
DBNPA: 2,2-dibromo-3-nitrilopropionamide
DDINO: Dideoxyinosine
DEPHA: bis(2-ethylhexyl)phosphoric acid
DMASA: Succinic acid 2,2-dimethylhydrazide

    ***

EB: Ethylbenzene
EG: Ethylene glycol
EO: Ethylene oxide or Ethoxyquin

    ***

EBA: Ethylbenzylaniline
ECA: Ethyl cyanoacrylate
EDB: 1,2-dibromoethane
EDC: 1,2-dichloroethane or 1-(3-(dimethylamino)propyl)-3-ethyl-carbodiimide hydrochloride
EGM: 2-methoxyethanol
EMA: Ethyl methacrylate
EMQ: Ethoxyquin
EMS: Ethyl methanesulfonate

    ***

EDAP: 1-(3-(dimethylamino)propyl)-3-ethyl-carbodiimide hydrochloride
EDTA: Ethylenediaminetetraacetic acid
EGME: 2-methoxyethanol
EPTC: Eptam
ETOC: Prallethrin

    ***

FU: 5-fluorouracil

    ***

FAA: 2-acetamidofluorene
FMN-Na: Riboflavin-5'-phosphate sodium salt dihydrate

    ***

FDNB: 2,4-dinitrofluorobenzene
FDUR: 5-fluorodeoxyuridine
FUDR: 5-fluorodeoxyuridine

    ***

GBHA: Glyoxal-bis(2-hydroxyanil)

    ***

HD: Mustard gas
HS: Mustard gas

    ***

HCB: Hexachlorobenzene
HCZ: Hydrochlorothiazide
HMD: Oxymetholone
HPT: Hexamethylphosphoramide

    ***

HABA: 2-(4-hydroxyphenylazo) benzoic acid
HBTU: 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate
HCBD: Hexachlorobutadiene
HCTZ: Hydrochlorothiazide
HFIP: 1,1,1,3,3,3-hexafluoro-2-propanol
HHDN: Aldrin
HMPA: Hexamethylphosphoramide
HMPT: Hexamethylphosphoramide
HMTA: Hexamethylenetetramine
HOBt: N-hydroxybenzotriazole

    ***

HEMPA: Hexamethylphosphoramide

    ***

IBN: Isobutyl nitrite
IMS: Methylated spirit

    ***

IDPN: 3,3'-iminodipropionitrile
IPDI: Isophorone diisocyanate

    ***

LEA: Triethylene glycol monodecyl ether

    ***

MC: 3-methylcholanthrene

    ***

MBI: Methylene diphenyl diisocyanate
MBK: 2-hexanone
MBT: 2-mercaptobenzothiazole
MCA: 3-methylcholanthrene
MDA: 4,4'-methylenedianiline
MDI: Methylene diphenyl diisocyanate
MEA: 2-methylaminoethanol
MEG: Ethylene glycol
MEK: Methyl ethyl ketone
MEP: 2-methyl-5-ethylpyridine
MES: Methylethyl sulfide or Morpholinoethanesulfonic acid
MIC: Methyl isocyanate
MIK: Methyl isobutyl ketone
MMC: Methylmercury chloride
MME: Methyl methacrylate
MMH: Methyl hydrazine
MMS: Methyl methanesulfonate
MMT: manganese methylcyclopentadienyl tricarbonyl
MNG: N-methyl-N-nitroso-N'-nitroguanidine
MPA: Medroxyprogesterone acetate
MPK: Acetophenone or 2-pentanone
MSA: Methanesulfonic acid
MSG: Monosodium glutamate
MSP: Monosodium phosphate

    ***

MBBA: Cytembena
MBOCA: 4,4'-methylenebis(2-chloroaniline)
MDAC: 7-diethylamino-4-methylcoumarin
MECB: Diethylene glycol monomethyl ether
MEHQ: 4-methoxyphenol
MEKP: Methyl ethyl ketone peroxide
MIBC: 4-methyl-2-pentanol
MIBK: Methyl isobutyl ketone
MNBK: 2-hexanone
MNNG: N-methyl-N-nitroso-N'-nitroguanidine
MOPS: 4-morpholinepropanesulfonic acid
MPBA: 3-phenoxybenzyl alcohol
MTBE: t-butyl methyl ether

    ***

NG: N-methyl-N-nitroso-N'-nitroguanidine

    ***

NAN: N-acetylneuraminic acid
NEA: N-nitroso-N-ethylaniline
NMP: N-methylpyrrolidone
NNK: 4-(methylnitrosoamino)-1-(3-pyridinyl)-1-butanone
NNN: N-nitrosonornicotine
NTA: Nitrilotriacetic acid

    ***

NANA: N-acetylneuraminic acid
NAZA: hexahydrocyclopenta[c]pyrrol-2(1H)-amine
NDMA: N-nitrosodimethylamine

    ***

NOHFAA: N-hydroxy-2-acetylaminofluorene

    ***

ODA: 4,4'-oxydianiline
ODB: 1,2-dichlorobenzene
OHB: Salicylamide
ONP: 2-nitrophenol

    ***

OCBA: 2-chlorobenzoic acid
ODCB: 1,2-dichlorobenzene
ONCB: 1-chloro-2-nitrobenzene

    ***

PAA: Peroxyacetic acid or Polyacrylamide
PAL: l-phenylalanine
PAN: 1-(2-pyridylazo)-2-naphthol
PBN: Boron nitride
PBZ: Parbendazole
PCC: Pyridinium chlorochromate
PCP: Pentachlorophenol or Phencyclidine
PCT: 4-chlorotoluene
PDT: 1-phenyl-3,3-dimethyltriazine
PET: polyethylene terephthalate
PGA: Folic acid
PGE: Phenyl glycidyl ether
PMA: Phenylmercuric acetate
PMK: Acetophenone
PNA: p-nitroaniline
PPD: p-phenylenediamine
PPO: Polyphenylene oxide
PQD: p-quinone dioxime
PTC: 1-phenyl-2-thiourea
PTU: 1-phenyl-2-thiourea
PVA: Poly(vinyl alcohol)
PVB: Polyvinyl butyral
PVP: Polyvinylpyrrolidine

    ***

PCAD: 4-chlorobenzaldehyde
PCBA: 4-chlorobenzoic acid
PCBC: 4-chlorobenzoyl chloride
PCMC: 4-chloro-3-methylphenol
PCMX: 4-chloro-3,5-dimethylphenol
PCON: 4-chloro-2-nitroaniline
PDMT: 1-phenyl-3,3-dimethyltriazine
PEMA: 2-phenyl-2-ethylmalondiamide
PETP: Pentaerythritol or Polyethylene terephthalate
PFOA: Pentadecafluorooctanoic acid
PGME: Propylene glycol monomethyl ether
PMAC: Phenylmercuric acetate
PMMA: Poly(methyl methacrylate)
PNBA: p-nitrobenzoic acid
PNCB: 4-chloronitrobenzene
PNSP: 4-nitrophenol sodium salt
POPG: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphorylglycerol, sodium salt
PSML: Tween 20
PTFE: Polytetrafluoroethylene
P-TSA p-toluenesulfonic acid monohydrate
PVDC: Polyvinylidene chloride

    ***

PCONA: 4-chloro-2-nitroaniline
PGMEA: Propylene glycol monomethyl ether acetate

    ***

QDO: p-quinone dioxime

    ***

RDGE: Diglycidylresorcinol ether

    ***

SA: Salicylic acid

    ***

SAH: Salicyladehyde
SAX: Salicylic acid
SET: Thimerosal
SOS: Sodium n-octyl sulfate
SPH: Hyaluronic acid sodium

    ***

SHMP: Sodium hexametaphosphate
SOPP: 2-phenylphenol sodium salt tetrahydrate
STPP: Sodium tripolyphosphate

    ***

TC: Tetraphenylcyclopentadienone (tetracyclone)

    ***

TAA: Thioacetamide
TAC: Triallyl cyanurate
TAT: Triethylenemelamine
TBT: p-tert-butyltoluene
TCC: Trichlorocarbanilide
TCP: 2,4,6-trichlorophenol or 2,3,4,6-tetrachlorophenol or Tricresyl phosphate
TEA: Tetraethylammonium bromide
TEL: Tetraethyl lead
TEM: Triethylenemelamine
TEN: Triethylamine
TEP: Triethyl phosphate
TET: Triethylenemelamine
TFE: 2,2,2-trifluoroethanol
THF: Tetrahydrofuran
THU: Thiourea
TMG: 1,1,3,3-tetramethylguanidine
TML: Tetramethyl lead
TMS: Tetramethyl silane
TNM: Tetranitromethane
TNT: 2,4,6-trinitrotoluene
TOF: Tris(2-ethylhexyl) phosphate
TPA: Terephthalic acid
TPP: Triphenyl phosphate
TRP: Tryptophan
TSC: Thiosemicarbazide
TTC: 2,3,5-triphenyl-2H-tetrazolium chloride
TTN: Thallic nitrate, trihydrate

    ***

TAIC: 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6(1H,3H,5H)trione
TBAB: Tetrabutylammonium bromide
TBEP: Tris(2-butoxyethyl)phosphate
TBHQ: Tert-butyl hydroquinone
TBME: t-butyl methyl ether
TCEP: Tris(2-chloroethyl)phosphate
TCNQ: 7,7,8,8-tetracyanoquinodimethane
TCPP: Tris(1,3-dichloro-2-propyl)phosphate
TEAB: Tetraethylammonium bromide
TEBA: Triethylbenzylammonium chloride
TEHP: Tris(2-ethylhexyl) phosphate
THME: Pentaerythritol
TIBP: Triisobutyl phosphate
TMAH: Tetramethylammonium hydroxide
TMAI: Tetramethylammonium iodide
TMAN: Trimellitic anhydride
TMHQ: Trimethylhydroquinone
TMPD: N,N,N',N'-tetramethyl-p-phenylenediamine dihydrochloride
TMTD: Thiram
TOPO: Trioctylphosphine oxide
TPTZ: 2,3,5-triphenyl-2H-tetrazolium chloride
TSPA: Tris(aziridinyl)phosphine sulfide
TSPP: Sodium pyrophosphate

    ***

TEBAC: Triethylbenzylammonium chloride
TEMED: N,N,N',N'-tetramethylethylenediamine
TMBAC: Benzyltrimethylammonium chloride
TMEDA: N,N,N',N'-tetramethylethylenediamine

    ***

TREGDA: Triethyleneglycol diacrylate

    ***

VC: Vinyl chloride

    ***

VCM: Vinyl chloride
VCR: Vincristine
VDC: 1,1-dichloroethylene (vinylidene chloride)

    ***

WSC: 1-(3-(dimethylamino)propyl)-3-ethyl-carbodiimide hydrochloride

***

Further web sites containing abbreviations:

Name Reaction In Organic Chemistry

  1. Baeyer-Villiger oxidation

  2. Barbier reaction

  3. **Barton-McCombie deoxygenation

  4. Baylis-Hillman reaction

  5. **Beckmann rearrangement

  6. Bergman cyclization

  7. Birch reduction

  8. Bischler-Napieralski isoquinoline synthesis

  9. Chan rearrangement

  10. Chichibabin reaction

  11. Claisen condensation

  12. Claisen rearrangement (traditional)

  13. Claisen rearrangement (Eschenmoser variant or Eschenmoser-Claisen)

  14. Claisen rearrangement (Johnson variant or ortho ester variant)

  15. oxy-Cope rearrangement

  16. Corey-Winter reaction

  17. Curtius rearrangement

  18. Danishefsky's diene

  19. **Darzens condensation

  20. **Demjanov rearrangement

  21. Dess Martin periodinane oxidation

  22. **Dieckmann condensation

  23. **Diels-Alder reaction

  24. **Favorskii rearrangement

  25. Fétizon's reagent

  26. carbon-Ferrier rearrangement

  27. Finkelstein reaction

  28. Fisher indole reaction

  29. **Fleming-Tamao oxidation

  30. Friedel Crafts acylation

  31. Friedel Crafts alkylation

  32. **Fries rearrangement

  33. **Fritsch-Buttenberg-Wiechell rearrangement

  34. **Gabriel synthesis

  35. Garner aldehyde

  36. Glaser reaction

  37. **Grignard reaction

  38. **Grob fragmentation

  39. Haller-Bauer reaction

  40. Heck reaction

  41. Henry reaction

  42. Hofmann elimination

  43. Hofmann rearrangement

  44. Horner-Wadsworth-Emmons olefination

  45. Jones oxidation

  46. **Julia epoxidation

  47. Keck allylation

  48. Knoevenagel condensation

  49. **Kulinkovich reaction

  50. **Luche reduction

  51. Majetich cyclobutane annulation

  52. **McMurry coupling

  53. Michael addition

  54. Mitsunobu reaction

  55. Mosher's acid - determine enantiomeric composition

  56. Nazarov cyclization

  57. Neber reaction

  58. **Nysted reagent (olefination of carbonyls)

  59. Parikh-Doering oxidation

  60. Paterno-Buchi cyclization

  61. Pauson-Khand reaction

  62. Pearlman's catalyst

  63. **Payne rearrangement

  64. **Pechmann condensation

  65. **Peterson olefination

  66. **Pictet-Spengler Cyclization

  67. **Ramberg-Bäcklund rearrangement

  68. Raney nickel

  69. **Reformatsky reaction

  70. **Robinson annulation

  71. Roush coupling

  72. **Schmidt reaction

  73. Schwartz reagent

  74. Seyferth-Gilbert homologation

  75. Shapiro reaction

  76. Sharpless asymmetric dihydroxylation

  77. Simmons-Smith reaction

  78. Sonogashira coupling

  79. Stevens rearrangement

  80. Stille coupling

  81. Stobbe condensation

  82. **Suzuki coupling

  83. Swern oxidation

  84. Tebbe reagent

  85. **Tiffeneau-Demjanov rearrangement

  86. Tishchenko reaction

  87. **Ugi condensation

  88. Vilsmeier formylation

  89. Wagner-Meerwein rearrangement

  90. **Willgerodt-Kindler reaction

  91. Wilkinson's catalyst

  92. Wittig olefination

  93. Wittig rearrangement ([2,3]-sigmatropic rearrangement)

  94. Wolf-Kishner reduction

  95. Zimmerman-Traxler transition state model

Reagents

A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction or is added to see if a reaction occurs " [1]. Such a reaction is used to confirm the presence of another substance. Examples of such analytical reagents include Fehling's reagent, Millon's reagent and Tollens' reagent.
Although the terms reactant and reagent are often used interchangeably, a reactant is more specifically a "substance that is consumed in the course of a chemical reaction" [1].Solvents and catalysts, although they are involved in the reaction, are usually not referred to as reactants. In organic chemistry, reagents are compounds or mixtures, usually composed of inorganic or small organic molecules, that are used to affect a transformation on an organic substrate. Examples of organic reagents include the Collins reagent, Fenton's reagent, and Grignard reagent.
In another use of the term, when purchasing or preparing chemicals, reagent-grade describes chemical substances of sufficient purity for use in chemical analysis, chemical reactions or physical testing. Purity standards for reagents are set by organizations such as ASTM International. For instance, reagent-quality water must have very low levels of impurities like sodium and chloride ions, silica, and bacteria, as well as a very high electrical resistivity.

More from Wikipedia: Reagents for organic chemistry

Oxides -Wikipedia

An oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are considered to be pure elements often contain a coating of oxides. For example, aluminium foil has a thin skin of Al2O3 that protects the foil from further corrosion.
Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements - lithium, sodium, potassium, rubidium, caesium, strontium and barium - react rapidly, even dangerously, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, and solutions of potassium and sodium, so called NaK are used to deoxygenate and dehydrate some organic solvents. The surface of most metals consists of oxides and hydroxides in the presence of air. A well known example is aluminium foil, which is coated with a thin film of aluminium oxide that passivates the metal, slowing further corrosion. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising. Although solid magnesium and aluminium react slowly with oxygen at STP, they, like most metals, will burn in air, generating very high temperatures. As a consequence, finely grained powders of most metals can be dangerously explosive in air.
In dry oxygen, iron readily forms iron(II) oxide, but the formation of the hydrated ferric oxides, Fe2O3−2x(OH)x, that mainly comprise rust, typically requires oxygen and water. The production of free oxygen by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe2O3 in the economically-important iron ore hematite.
Due to its electronegativity, oxygen forms chemical bonds with almost all elements to give the corresponding oxides. So-called noble metals (common examples: gold, platinum) resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes.

Insolubility in water

The oxide ion, O2−, is the conjugate base of the hydroxide ion, OH, and is encountered in ionic solid such as calcium oxide. O2− is unstable in aqueous solution − its affinity for H+ is so great (pKb ~ −22) that it abstracts a proton from a solvent H2O molecule:
O2− + H2O → 2 OH

Nomenclature

In the 18th century, oxides were named calxes or calces after the calcination process used to produce oxides. Calx was later replaced by oxyd.
Oxides are usually named after the number of oxygen atoms in the oxide. Oxides containing only one oxygen are called oxides or monoxides, those containing two oxygen atoms are dioxides, three oxygen atoms makes it a trioxide, four oxygen atoms are tetroxides, and so on following the Greek numerical prefixes. In the older literature and continuing in industry, oxides are named by contracting the element name with "a." Hence alumina, magnesia, chromia, are, respectively, Al2O3, MgO, Cr2O3.
Two other types of oxide are peroxide, O22−, and superoxide, O2. In such species, oxygen is assigned higher oxidation states than oxide.

Types of oxides

Oxides of more electropositive elements tend to be basic. They are called basic anhydrides; adding water, they may form basic hydroxides. For example, sodium oxide is basic; when hydrated, it forms sodium hydroxide.
Oxides of more electronegative elements tend to be acidic. They are called acid anhydrides; adding water, they form oxoacids. For example, dichlorine heptoxide is acid; perchloric acid is a more hydrated form.
Some oxides can act as both acid and base at different times. They are amphoteric. An example is aluminium oxide. Some oxides do not show behavior as either acid or base.
The oxides of the chemical elements in their highest oxidation state are predictable and the chemical formula can be derived from the number of valence electrons for that element. Even the chemical formula of O4, tetraoxygen, is predictable as a group 16 element. One exception is copper for which the highest oxidation state oxide is copper(II) oxide and not copper(I) oxide. Another exception is fluoride that does not exist as expected as F2O7 but as OF2.[1] Since F is more electronegative than O, OF2 does not represent an oxide of fluorine, but instead represents a fluoride of oxygen. Phosphorus pentoxide, the third exception is not properly represented by the chemical formula P2O5 but by P4O10.

List of all known oxides sorted by oxidation state

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