Chemistry:Double bond rule

From HandWiki
Short description: Chemistry rule: elements of period ≥ 3 only form single bonds

In chemistry, the double bond rule states that elements with a principal quantum number (n) greater than 2 for their valence electrons (period 3 elements and higher) tend not to form multiple bonds (e.g. double bonds and triple bonds).[1] The double bonds, when they exist, are often weak due to poor orbital overlap between the n>2 orbitals of the two atoms. Although such compounds are not intrinsically unstable, they instead tend to polymerize. An example is the rapid polymerization that occurs upon condensation of disulfur, the heavy analogue of O
2
. Numerous exceptions to the rule exist.[2]

Double bonds for carbon and nearest neighbours
B
boron
(n=2)
C
carbon
(n=2)
N
nitrogen
(n=2)
O
oxygen
(n=2)
Si
silicon
(n=3)
P
phosphorus
(n=3)
S
sulfur
(n=3)
B diborenes alkylideneboranes aminoboranylidenes, rare[3] oxoboranes, rare,
rapid oligomerization[4]
borasilenes (rare)[5] boranylidenephosphanes, rare, stable compounds are known[6] thioxoboranes, rare[7]
C alkenes imines carbonyls silenes phosphaalkenes thioketones
N azo compounds nitroso compounds silanimines, rare, easy oligomerization, observed only at low temp[8] phosphazene (P=N) sulfilimines
O Singlet oxygen silanones, Si=O bonds extremely reactive, oligomerization to siloxanes numerous, e.g. phosphine oxides, phosphonates, phosphinates,
phosphates
sulfinyls
Si disilenes silylidenephosphanes a.k.a. phosphasilenes, rare[9] silanethiones, rare, easy oligomerization[10]
P diphosphenes common compounds such as thiophosphates and phosphine sulfides, for example, triphenylphosphine sulfide and certain dithiadiphosphetanes
S disulfur, thiosulfoxides

Triple bonds

Triple bonds for carbon and nearest neighbours
B
boron
(n=2)
C
carbon
(n=2)
N
nitrogen
(n=2)
O
oxygen
(n=2)
Si
silicon
(n=3)
P
phosphorus
(n=3)
S
sulfur
(n=3)
Ge
germanium
(n=4)
As
arsenic
(n=4)
B diborynes Borataalkynes have been observed[11] Observed in (t-Bu)BN(t-Bu) (an iminoborane)
C alkynes cyanides Carbon monoxide (C≡O) silynes phosphaalkynes Carbon monosulfide (C≡S) arsaalkynes
N Dinitrogen, Diazonium Phosphorus mononitride (P≡N) Arsa-diazonium[12]
O Silicon monoxide has some triple-bond character
Si disilynes
P Diphosphorus
S Observed in (I
2
)
2
S2+
2
[13]
Ge Digermyne
As Arsenic monophosphide (As≡P)

Other meanings

Another unrelated double bond rule exists that relates to the enhanced reactivity of sigma bonds attached to an atom adjacent to a double bond. In bromoalkenes, the C–Br bond is very stable, but in an allyl bromide, this bond is very reactive. Likewise, bromobenzenes are generally inert, whereas benzylic bromides are reactive. The first to observe the phenomenon was Conrad Laar in 1885. The name for the rule was coined by Otto Schmidt in 1932.[14][15]

References

  1. Jutzi, Peter (1975). "New Element‐Carbon (p‐p)π Bonds". Angewandte Chemie International Edition in English 14 (4): 232–245. doi:10.1002/anie.197502321. 
  2. West, Robert (2002). "Multiple bonds to silicon: 20 years later". Polyhedron 21 (5–6): 467–472. doi:10.1016/S0277-5387(01)01017-8. 
  3. Some research has been done on isomerization of B=NH2 to triple-bonded iminoborane HBNH Rosas-Garcia, Victor M.; Crawford, T. Daniel (2003). "The aminoboranylidene–iminoborane isomerization". The Journal of Chemical Physics 119 (20): 10647–10652. doi:10.1063/1.1620498. Bibcode2003JChPh.11910647R. 
  4. Vidovic, Dragoslav; Moore, Jennifer A.; Jones, Jamie N.; Cowley, Alan H. (2005). "Synthesis and Characterization of a Coordinated Oxoborane: Lewis Acid Stabilization of a Boron−Oxygen Double Bond". Journal of the American Chemical Society 127 (13): 4566–4567. doi:10.1021/ja0507564. PMID 15796509. 
  5. Franz, Daniel; Szilvási, Tibor; Pöthig, Alexander; Inoue, Shigeyoshi (2019). "Isolation of an N‐Heterocyclic Carbene Complex of a Borasilene". Chemistry – A European Journal 25 (47): 11036–11041. doi:10.1002/chem.201902877. PMID 31241215. 
  6. Example: Ar*P=B(TMP)2, where Ar* is 2,6-dimesityl-phenyl and TMP is 2,2,6,6-tetramethylpiperidine; see Rivard, Eric; Merrill, W. Alexander; Fettinger, James C.; Wolf, Robert; Spikes, Geoffrey H.; Power, Philip P. (2007). "Boron−Pnictogen Multiple Bonds: Donor-Stabilized PB and AsB Bonds and a Hindered Iminoborane with a B−N Triple Bond". Inorganic Chemistry 46 (8): 2971–2978. doi:10.1021/ic062076n. PMID 17338516. 
  7. Tokitoh, Norihiro; Ito, Mitsuhiro; Okazaki, Renji (1996). "Formation and reactions of a thioxoborane, a novel boron-sulfur double-bond compound". Tetrahedron Letters 37 (29): 5145–5148. doi:10.1016/0040-4039(96)01039-8. 
  8. Zigler, Steven S.; West, Robert; Michl, Josef (1986). "Observation of a Silanimine in an Inert Matrix and in Solution at Low Temperature". Chemistry Letters 15 (6): 1025–1028. doi:10.1246/cl.1986.1025. 
  9. Example: Ar*tBuSi=PAr*, where Ar* is 2,4,6-trisiopropylphenyl and tBu is tert-butyl; see Driess, M.; Rell, S.; Merz, K. (1999). "Ungewöhnliche Reaktivität der Silicium-Phosphor-Doppelbindung in einem Silyliden(fluorsilyl)phosphan: Intramolekulare C,H-Inserierung und seine Umwandlung in ein neues Silyliden(silyl)phosphan". Zeitschrift für Anorganische und Allgemeine Chemie 625 (7): 1119–1123. doi:10.1002/(SICI)1521-3749(199907)625:7<1119::AID-ZAAC1119>3.0.CO;2-1. 
  10. Suzuki, Hiroyuki; Tokitoh, Norihiro; Nagase, Shigeru; Okazaki, Renji (1994). "The First Genuine Silicon-Sulfur Double-Bond Compound: Synthesis and Crystal Structure of a Kinetically Stabilized Silanethione". Journal of the American Chemical Society 116 (25): 11578–11579. doi:10.1021/ja00104a052. 
  11. Allwohn, Jürgen; Pilz, Monika; Hunold, Ralf; Massa, Werner; Berndt, Armin (1990). "Compounds with a Boron–Carbon Triple Bond". Angew. Chem. Int. Ed. Engl. 29 (9): 1032–1033. doi:10.1002/anie.199010321. 
  12. Kuprat, Marcus; Schulz, Axel (2013). "Arsa-Diazonium Salts With an Arsenic–Nitrogen Triple Bond". Angew. Chem. Int. Ed. Engl. 52 (28): 7126–7130. doi:10.1002/anie.201302725. PMID 23740867. 
  13. Ritter, Stephen K. (March 21, 2005). "Sulfur's Turn for Multiple Bonds". Chemical & Engineering News. https://cen.acs.org/articles/83/i12/SULFURS-TURN-MULTIPLE-BONDS.html. 
  14. Schmidt, Otto (1932). "Über den Ort der Sprengung von C—C-Bindungen in Kettenmolekülen". Zeitschrift für Physikalische Chemie 159A: 337–356. doi:10.1515/zpch-1932-15931. 
  15. Hoogenboom, Bernard E. (1998). "A History of the Double-Bond Rule". Journal of Chemical Education 75 (5): 596. doi:10.1021/ed075p596. Bibcode1998JChEd..75..596H.