| Overview: The general form of the SN2 mechanism is as follows:  nuc: = nucleophile X = leaving group (usually halide or tosylate) The SN2 reaction involves displacement of a leaving group (usually a halide or a tosylate), by a nucleophile. This reaction works the best with methyl and primary halides because bulky alkyl groups block the backside attack of the nucleophile, but the reaction does work with secondary halides (although it is usually accompanied by elimination), and will not react at all with tertiary halides. In the following example, the hydroxide ion is acting as the nucleophile and bromine is the leaving group:  Because of the backside attack of the nucleophile, inversion of configuration occurs.  Solvents: Protic solvents such as water and alcohols stabilize the nucleophile so much that it won't react. Therefore, a good polar aprotic solvent is required such as ethers and ketones and halogenated hydrocarbons. Nucleophiles: A good nucleophile is required since it is involved in the rate-determining step. Leaving groups: A good leaving group is required, such as a halide or a tosylate, since it is involved in the rate-determining step. |
2012년 12월 21일 금요일
SN2
SN2 Mechanism
2012년 12월 20일 목요일
alanine ester
L-Alanine, N-acetyl-, 1-methyl-2-(methylamino)-2-oxoethyl ester, (S)-
| 상품명칭: | L-Alanine, N-acetyl-, 1-methyl-2-(methylamino)-2-oxoethyl ester, (S)- |
| CAS 레지스트리 번호: | 32991-01-8 |
| 분자 구조: |  |
| 분자식: | C9H16N2O4 |
Aldol Condensation Mechanism
Aldol Condensation Mechanism
Answered »
Can someone write out the mechanism aldol condensation forthis reaction.
the equation is Benzil + Dibenzyl Ketone ->1,2,3,4-Tetraphenylcyclopentadienone + 2 H2O
2012년 12월 16일 일요일
2012년 12월 14일 금요일
isopropyl benzoate
2010학년도 의.치의학교육입문검사(MEET)
제3교시 자연과학추론II 의학계열(짝수형)
28. 그림은 isopropyl benzoate의 반응식과 주생성물 B의 IR, 1H-NMR 및 13C-NMR 스펙트럼이다. (단, NMR 스펙트럼은 CDCl3를 용매로 사용하여 얻었다.)
반응조건 A로 가장 적절한 것은?
정답 : 2번
스펙트럼 해석 결과, 주생성물 B는 벤질 알코올(benzyl alcohol)이며, 자세한 풀이는 1주일 후에 공개하겠습니다.
에스테르의 환원 반응에 대해 찾아보세요.
에스테르는 에스테르의 가수소분해(hydrogenolysis of esters) 반응에 의해 환원될 수 있으며, 그 결과 1차 알코올이 생성됩니다.
The
hydrogenolysis of esters to alcohols is a reaction between esters and
hydrogen which selectively splits a C-0 bond adjacent to a carbonyl
group.
Lithium aluminium hydride (LiAlH4 or LAH)
* Lithium aluminium hydride, LiAlH4, also abbreviated as LAH, is a reducing agent commonly employed in modern organic synthesis.
* It is a nucleophilic reducing agent, best used to reduce polar multiple bonds like C=O.
*
LiAlH4 can reduce aldehydes to primary alcohols, ketones to secondary
alcohols, carboxylic acids and esters to primary alcohols, amides and
nitriles to amines, epoxides to alcohols and lactones to diols.
* LiAlH4 is a powerful reducing agent than sodium borohydride, NaBH4 since the Al-H bond is weaker than B-H bond.
Structure of Lithium aluminium hydride
Mechanism of Reduction by Lithium aluminium hydride
Reduction of Esters to primary alcohols: The ester is first converted to aldehyde which is further reduced to primary alcohol.
(to be continued)
IR 스펙트럼에서 얻을 수 있는 정보
1. 3300 broad peak -> -OH 신축 진동
2. 3000 이상 =C-H, 3000 이하 -C-H 신축 진동
종합하면, 탄소-탄소 이중 결합(또는 방향족) 및 탄소-탄소 단일 결합이 존재하는 알코올 화합물일 것이다.
PMR 스펙트럼에서 얻을 수 있는 정보
1. 화학적 환경이 다른 3종류의 수소가 존재한다.
2. 약 7.3 ppm peak -> 벤젠 고리에 붙어있는 H
3. 나머지 2개중 1개는 알코올(-OH)에 붙어있는 H
CMR 스펙트럼에서 얻을 수 있는 정보
1. 화학적 환경이 다른 5종류의 탄소가 존재한다.
2. 120~150 ppm 4 peaks -> 벤젠 고리를 이루는 C -> 4개 peak로 봐서 수소 1개가 다른 원자로 치환된 페닐기에 의한 것이다.
3. 나머지 1개는, IR & PMR 정보와 결합하면, -CH- 또는 -CH2-
그래서 내린 결론이 벤질 알코올입니다.
NMR 스펙트럼의 상세한 피크 어싸인먼트는 아래와 같습니다.
에틸 알코올(ethyl alcohol)의 NMR 스펙트럼과 한 번 비교해 보세요.
2012년 12월 13일 목요일
heteronuclear Diatomic Molecules orbital
p - p => 시그마 1, 파이 2
s - p => 시그마 1
HCl is a simple heteronuclear diatomic molecule. The valence ao’s for this molecule are simply the H 1s and the 3s, 3px, 3py, 3pz ao’s of chlorine.
This following are the molecular orbital energy levels diagram of hydrogen chloride....
HCl has four pairs of valence electrons, yields the electronic configuration
(3s)2 (σ3px)2 (π3py)2 (π3pz)2 (σ3p*)
And shows three lone pairs (the 3s and pπn pairs) and one bond pair (from pσ)
here is the HF orbital diagram..
Do rate if useful...
hen two atomic orbitals make one molecular orbital there must be an antibonding orbital also. Why should they make also an antibonding molecular orbital.
s - p => 시그마 1
HCl is a simple heteronuclear diatomic molecule. The valence ao’s for this molecule are simply the H 1s and the 3s, 3px, 3py, 3pz ao’s of chlorine.
This following are the molecular orbital energy levels diagram of hydrogen chloride....
HCl has four pairs of valence electrons, yields the electronic configuration
(3s)2 (σ3px)2 (π3py)2 (π3pz)2 (σ3p*)
And shows three lone pairs (the 3s and pπn pairs) and one bond pair (from pσ)
here is the HF orbital diagram..
Do rate if useful...
hen two atomic orbitals make one molecular orbital there must be an antibonding orbital also. Why should they make also an antibonding molecular orbital.
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