the NMR spectrum of caffeine

The white powder evaporates while curing the tea in the electric heater was collected and investigated using the 1H NMR.



The scanned picture is not distinct enough. I'll try scan it again.
Both the chemical shift and the peak integral of the spectrum matches perfectly with the caffeine spectrum.
It is a strong evidence to show that the caffeine will evaporate from the raw tea during the curing process.



According to SDBS, the chemical shift for caffeine are 7.512, 3.997, 3.584 and 3.407. The experimental data for the white powder are perfectly matched with the caffeine database.



The more clearer view of NMR spectrum will be posted while I have more time.

liquid crystal

Reinitzer porposed three important feature of cholesteric liquid crystal:
1. the existance of two melting points
2. the reflection of circular polarized light
3. the ability to rotate of polarization direction of light

Types of liquid crystal:
1. thermotropic liquid crystal
a. smectic
b. nematic
c. cholesteric (chiral nematic)
d. discotic
2. lyotropic liquid crystal


液晶的特徵
1. 存在兩個熔點
2. 反射圓柱偏振光
3. 旋轉偏振光的方向

液晶的種類
1. 向熱性（熱致性）
a. 層列相
b. 向列相
c. 膽固醇相 (手性向列相)
d. 柱狀相
2. 向液性（溶致性）

ref: http://en.wikipedia.org/wiki/Liquid_crystal

Why do some compounds adsorb water from air?

1. ionic compounds:
a. coulomb interaction
i. cation: Mⁿ⁺
ii. anion: SO₄^2-, NO₃^-
iii. both cation and anion: CuSO₄‧5H2O
b. deliquescence
hydroxide (OH^-)
2. porous materials: capillary condensation
zeolites (SiO₂)

1. 離子化合物
a. 庫倫作用力
i. 陽離子
ii. 陰離子
iii. 陽離子及陰離子
b. 潮解
2. 孔洞材料

ref: http://antoine.frostburg.edu/chem/senese/101/compounds/faq/why-hygroscopic.shtml

chemical compounds in Camellia sinensis var sinensis (tea plant) - phenolic flavan-3-ols

R = H, (+)-catechin, C

R = OH, (+)-gallocatechin, GC

R = H, (-)-epicatechin, EC

R = OH, (-)- epigallocatechin, EGC

R = H, (-)-epicatechin-3-O-gallate, ECG

R = OH, (-)-epigallocatechin-3-O-gallate, EGCG