x*****c
发帖数: 1005 | 1 核磁氢谱上许多峰出现宽峰或者是积分不足时因为该氢的驰豫时间T1很长，比如二乙胺，
通常核磁中 D1=5T1（最长的一个氢核），这样各个氢积分应该能达到相同
各个碳也是类似的。
有没有数据库收集这个T1的？ |
e****2
发帖数: 2723 | 2 这个表观是该如何解释才直观那?
是不是因为氢的电磁周围环境变化慢而被NMR纪录下来了?
胺，
【在 x*****c 的大作中提到】
: 核磁氢谱上许多峰出现宽峰或者是积分不足时因为该氢的驰豫时间T1很长，比如二乙胺，
: 通常核磁中 D1=5T1（最长的一个氢核），这样各个氢积分应该能达到相同
: 各个碳也是类似的。
: 有没有数据库收集这个T1的？
|
x*****c
发帖数: 1005 | 3 恩，我觉得你的表述是合理。
如果驰豫时间长，氢信号还没来得及全部记录就再次跃迁，产生总信号就偏少了，反映
在核磁图上就是积分不足了
【在 e****2 的大作中提到】
: 这个表观是该如何解释才直观那?
: 是不是因为氢的电磁周围环境变化慢而被NMR纪录下来了?
:
: 胺，
|
e****2
发帖数: 2723 | 4 能否 解释是氢的运动被缓慢了?
这样在有限的时间里, 纪录了它的电磁环境变化
这样就变成了大宽峰
【在 x*****c 的大作中提到】
: 恩，我觉得你的表述是合理。
: 如果驰豫时间长，氢信号还没来得及全部记录就再次跃迁，产生总信号就偏少了，反映
: 在核磁图上就是积分不足了
|
e****2
发帖数: 2723 | 5 如果温度降低到-40 导致以前的比较细的C-H峰变成大包
原因如何解释?
胺，
【在 x*****c 的大作中提到】
: 核磁氢谱上许多峰出现宽峰或者是积分不足时因为该氢的驰豫时间T1很长，比如二乙胺，
: 通常核磁中 D1=5T1（最长的一个氢核），这样各个氢积分应该能达到相同
: 各个碳也是类似的。
: 有没有数据库收集这个T1的？
|
x*****c
发帖数: 1005 | 6 这个有多种因素吧，
我觉得与溶液的性质有关，另外氢核的热运动也大大降低
【在 e****2 的大作中提到】
: 如果温度降低到-40 导致以前的比较细的C-H峰变成大包
: 原因如何解释?
:
: 胺，
|
e****2
发帖数: 2723 | 7 氢键作用? C-H 这个作用比较小的
【在 x*****c 的大作中提到】
: 这个有多种因素吧，
: 我觉得与溶液的性质有关，另外氢核的热运动也大大降低
|
M****d
发帖数: 131 | 8 宽峰和积分面积是两回事情
面积偏低是因为t1长
宽峰是因为exchange rate慢
胺，
【在 x*****c 的大作中提到】
: 核磁氢谱上许多峰出现宽峰或者是积分不足时因为该氢的驰豫时间T1很长，比如二乙胺，
: 通常核磁中 D1=5T1（最长的一个氢核），这样各个氢积分应该能达到相同
: 各个碳也是类似的。
: 有没有数据库收集这个T1的？
|
M****d
发帖数: 131 | 9 温度低了exchange rate更低了
【在 e****2 的大作中提到】
: 如果温度降低到-40 导致以前的比较细的C-H峰变成大包
: 原因如何解释?
:
: 胺，
|
e****2
发帖数: 2723 | 10 EXCHANGE RATE 是指什么?
【在 M****d 的大作中提到】
: 温度低了exchange rate更低了
|
|
|
t******t
发帖数: 3045 | 11 broad NMR signals of macro molecules (polymers, proteins)are caused by very
fast relaxation, i.e. short t1. t1 of protons in most small molecules are a
few seconds. 13C especially carbonyl 13C that has no protons attached to
have much longer t1, that is why 13C NMR is not as quantitative as 1H NMR.
Unless you want to have very accurate results (errors < 3%), there is no
need to set the relaxation delay to ~5x t1 instead of 1x or 2x t1 since
your experiment run time will be much longer. |
t******t
发帖数: 3045 | 12 If you want to speed up the relaxation, you can use solvents with more
protons(i.e. not the deuterated solvents) or add things like Cr(acac)2. |
s********l
发帖数: 3 | 13 Is the exchange rate concentration-dependent as well? If so, does it mean
that the molecules interact each other by H-bond or others? Thanks.
【在 M****d 的大作中提到】
: 宽峰和积分面积是两回事情
: 面积偏低是因为t1长
: 宽峰是因为exchange rate慢
:
: 胺，
|
M****d
发帖数: 131 | 14 it differes case by case.
if the exchange is intramolecular, such as bond rotation or conformational
change, it can be concentration independent.
if any intermolecular processes,like self association or aggretation, are
involved, then sometimes change the concentration will be helpful.
there are other mechanisms for peak broadening as well.
【在 s********l 的大作中提到】
: Is the exchange rate concentration-dependent as well? If so, does it mean
: that the molecules interact each other by H-bond or others? Thanks.
|
M****d
发帖数: 131 | 15 i do not understand how broadening is related to t1.
with either fast or slow relaxation, the chemical shift position is well
defined. the intergration of a 13C carbonyl peak can be wildly off, but the
peak always appears to be a sharp peak.
the cause of broadening is, most of the times, the change in chemical
environment during the a certain period of time (say, 1-1000 ms). That means
, in the time window of observation, the nuclei in interest can appear at
different environments, and all these
【在 t******t 的大作中提到】
: broad NMR signals of macro molecules (polymers, proteins)are caused by very
: fast relaxation, i.e. short t1. t1 of protons in most small molecules are a
: few seconds. 13C especially carbonyl 13C that has no protons attached to
: have much longer t1, that is why 13C NMR is not as quantitative as 1H NMR.
: Unless you want to have very accurate results (errors < 3%), there is no
: need to set the relaxation delay to ~5x t1 instead of 1x or 2x t1 since
: your experiment run time will be much longer.
|
m****e
发帖数: 255 | 16 To answer the op's question: t1 is affected by a lot of factors: magnet
strength, sample solvent, sample concentration, etc. So it is almost
impossible to have a database for t1. T1 of your sample can be measured on
your NMR instrument. If t1 is important for your experiment, you need to
measure t1 before experiment. |
x*****c
发帖数: 1005 | 17 今天测出来乙醇的羟基氢的 d7是 2.3s,t1=1.4d7=3.22s,这个数据正常么？甲基氢d7是
1.0s，
t1=1.4s
这样检测时 将d1=5t1=16.1s 这样就可以进行准确的积分比较了，是么？
另外，通常碳的t1都很长，比如上百秒，除了反转门控技术已经加铬试剂（我做的课题
无法使
用，因为谱线重叠）外，
如果想发表paper，进行c谱定量大概要怎么做？有什么参考文献么？
我也是刚做核磁不久，许多道道搞不清楚
on
【在 m****e 的大作中提到】
: To answer the op's question: t1 is affected by a lot of factors: magnet
: strength, sample solvent, sample concentration, etc. So it is almost
: impossible to have a database for t1. T1 of your sample can be measured on
: your NMR instrument. If t1 is important for your experiment, you need to
: measure t1 before experiment.
|
x*****c
发帖数: 1005 | 18 我现在在做一个碳谱定量，
我只对两个碳的积分之比感兴趣，
我能否改变d1 比如从2s到10s，到20s 到更大，
如果这两个碳积分之比恒定了，那我就可以拿这个数据来写paper？
因为如果根据d1=5t1，有可能长达上千秒，一个scan就 十几分钟。
对了，如果我只对两个碳积分比感兴趣，
这个碳谱定量是不是一定得用反转门控？
我的是测乙醇羟基部分被氘代后，亚甲基峰出现两个，应该是一个氘代羟基乙醇（高场
），一个普通乙醇（低场），
我想通过碳谱来定量确定这两种化合物的浓度之比。
有没有相关的文献呢？ |
c******n
发帖数: 16403 | 19 你打算投什么杂志
【在 x*****c 的大作中提到】
: 我现在在做一个碳谱定量，
: 我只对两个碳的积分之比感兴趣，
: 我能否改变d1 比如从2s到10s，到20s 到更大，
: 如果这两个碳积分之比恒定了，那我就可以拿这个数据来写paper？
: 因为如果根据d1=5t1，有可能长达上千秒，一个scan就 十几分钟。
: 对了，如果我只对两个碳积分比感兴趣，
: 这个碳谱定量是不是一定得用反转门控？
: 我的是测乙醇羟基部分被氘代后，亚甲基峰出现两个，应该是一个氘代羟基乙醇（高场
: ），一个普通乙醇（低场），
: 我想通过碳谱来定量确定这两种化合物的浓度之比。
|
u***n
发帖数: 1263 | 20 j of magnetic resonance
【在 c******n 的大作中提到】
: 你打算投什么杂志
|
|
|
m***c
发帖数: 1403 | 21 that pd will be 5*t1, you won't save time on it
【在 x*****c 的大作中提到】
: 我现在在做一个碳谱定量，
: 我只对两个碳的积分之比感兴趣，
: 我能否改变d1 比如从2s到10s，到20s 到更大，
: 如果这两个碳积分之比恒定了，那我就可以拿这个数据来写paper？
: 因为如果根据d1=5t1，有可能长达上千秒，一个scan就 十几分钟。
: 对了，如果我只对两个碳积分比感兴趣，
: 这个碳谱定量是不是一定得用反转门控？
: 我的是测乙醇羟基部分被氘代后，亚甲基峰出现两个，应该是一个氘代羟基乙醇（高场
: ），一个普通乙醇（低场），
: 我想通过碳谱来定量确定这两种化合物的浓度之比。
|
b*******r
发帖数: 1073 | 22 ft. I typed in a lot of Chinese, but all gone. sorry for the poor English,
and correct me if what I said is wrong.
D7 is tao, I didn't get it, why T1 = 1.4 D7? How did you measure T1?
As previously said, T1 depends on many factors including temperature,
concentration sample state (degass or not, etc.), magnetic field ... your
values looks not too unmoral to me.(but you better read more papers)
serious quantitative 13C NMR does have many tricks, like instrumentation(
like shimming, pulse calibrat
【在 x*****c 的大作中提到】
: 今天测出来乙醇的羟基氢的 d7是 2.3s,t1=1.4d7=3.22s,这个数据正常么？甲基氢d7是
: 1.0s，
: t1=1.4s
: 这样检测时 将d1=5t1=16.1s 这样就可以进行准确的积分比较了，是么？
: 另外，通常碳的t1都很长，比如上百秒，除了反转门控技术已经加铬试剂（我做的课题
: 无法使
: 用，因为谱线重叠）外，
: 如果想发表paper，进行c谱定量大概要怎么做？有什么参考文献么？
: 我也是刚做核磁不久，许多道道搞不清楚
:
|
b*******r
发帖数: 1073 | 23 do you have the priliminary 13NMR spectrum right now?
【在 x*****c 的大作中提到】
: 我现在在做一个碳谱定量，
: 我只对两个碳的积分之比感兴趣，
: 我能否改变d1 比如从2s到10s，到20s 到更大，
: 如果这两个碳积分之比恒定了，那我就可以拿这个数据来写paper？
: 因为如果根据d1=5t1，有可能长达上千秒，一个scan就 十几分钟。
: 对了，如果我只对两个碳积分比感兴趣，
: 这个碳谱定量是不是一定得用反转门控？
: 我的是测乙醇羟基部分被氘代后，亚甲基峰出现两个，应该是一个氘代羟基乙醇（高场
: ），一个普通乙醇（低场），
: 我想通过碳谱来定量确定这两种化合物的浓度之比。
|
b*******r
发帖数: 1073 | 24 I think he was focusing on "being quantitative".
here it should be T2
one can use T2 filter to reduce/remove the signals from proteins in
metabolites mixtures, because those macromolecules have shorter T2 and
broader peakes
the
means
【在 M****d 的大作中提到】
: i do not understand how broadening is related to t1.
: with either fast or slow relaxation, the chemical shift position is well
: defined. the intergration of a 13C carbonyl peak can be wildly off, but the
: peak always appears to be a sharp peak.
: the cause of broadening is, most of the times, the change in chemical
: environment during the a certain period of time (say, 1-1000 ms). That means
: , in the time window of observation, the nuclei in interest can appear at
: different environments, and all these
|
x*****c
发帖数: 1005 | 25 已经上传附件
t-butanol 与氘代的羟基 乙醇混合物碳谱 d1=2，13CPD，普通测量法
注意到各个碳峰均有裂分，但在低场处分离比较明显，
每个峰归属于
普通t-butanol，氘代羟基t-butanol
普通ethanol，氘代羟基ethanol
我只关心 这两组的氢氘比
我该如何定量呢？
有没有相应的ref？
认为
【在 b*******r 的大作中提到】
: do you have the priliminary 13NMR spectrum right now?
|
x*****c
发帖数: 1005 | 26 就是将实验改为 测t1模式（一般核磁均有这个模式的设置）
不断改变d7，使想测量的位置的峰为0，读出此处的d7 则t1=1.4d7
processing.
【在 b*******r 的大作中提到】
: ft. I typed in a lot of Chinese, but all gone. sorry for the poor English,
: and correct me if what I said is wrong.
: D7 is tao, I didn't get it, why T1 = 1.4 D7? How did you measure T1?
: As previously said, T1 depends on many factors including temperature,
: concentration sample state (degass or not, etc.), magnetic field ... your
: values looks not too unmoral to me.(but you better read more papers)
: serious quantitative 13C NMR does have many tricks, like instrumentation(
: like shimming, pulse calibrat
|
t******t
发帖数: 3045 | 27 Just wanted to mention the relationship between line width and relaxation.
Line width is related to T2 while T2
is related to T1. If the relaxation in xy is slow, the relaxation in z is
also slow. The longer T2 is, the sharper
the peak is. The reason why NMR peaks are only a few Hz wide while UV-Vis
and IR peaks are much wider and
have to be measured by wavelength in nm is that the relaxations in these
spectroscopy are much faster.
The broadening caused by exchange is another story. If the excha
【在 M****d 的大作中提到】
: i do not understand how broadening is related to t1.
: with either fast or slow relaxation, the chemical shift position is well
: defined. the intergration of a 13C carbonyl peak can be wildly off, but the
: peak always appears to be a sharp peak.
: the cause of broadening is, most of the times, the change in chemical
: environment during the a certain period of time (say, 1-1000 ms). That means
: , in the time window of observation, the nuclei in interest can appear at
: different environments, and all these
|
t******t
发帖数: 3045 | 28 They should be a few seconds, so I don't think they are off. In fact, you
don't have to set d1 to 5T1, because
the relaxation also happens during acquisition. If your FID size is 32k for
5k Hz, then the acquisition time is
32k/5k/2= 3.2 seconds.
If you have a new way to do quantitation with carbon spectrum, you can
definitely publish your method.
【在 x*****c 的大作中提到】
: 今天测出来乙醇的羟基氢的 d7是 2.3s,t1=1.4d7=3.22s,这个数据正常么？甲基氢d7是
: 1.0s，
: t1=1.4s
: 这样检测时 将d1=5t1=16.1s 这样就可以进行准确的积分比较了，是么？
: 另外，通常碳的t1都很长，比如上百秒，除了反转门控技术已经加铬试剂（我做的课题
: 无法使
: 用，因为谱线重叠）外，
: 如果想发表paper，进行c谱定量大概要怎么做？有什么参考文献么？
: 我也是刚做核磁不久，许多道道搞不清楚
:
|
b*******r
发帖数: 1073 | 29 if you want the ratio of 普通t-butanol/氘代羟基t-butanol bu 13C NMR, (or 普
通ethanolvs 氘代羟基ethanol)
try to do a better job in inproving the resolution (that's why I asked you
the primilinary spectrum). it's difficult to intergrate seperately the two
very-close methyl C13 peakes. Some softwares may help you in intergrating
these two peaks. You can use the quandary carbon, but try to get better
resolved (almost to baseline) peaks if you can.
for quantification, try out several pulse sequences available i
【在 x*****c 的大作中提到】
: 已经上传附件
: t-butanol 与氘代的羟基 乙醇混合物碳谱 d1=2，13CPD，普通测量法
: 注意到各个碳峰均有裂分，但在低场处分离比较明显，
: 每个峰归属于
: 普通t-butanol，氘代羟基t-butanol
: 普通ethanol，氘代羟基ethanol
: 我只关心 这两组的氢氘比
: 我该如何定量呢？
: 有没有相应的ref？
: 认为
|
b*******r
发帖数: 1073 | 30 yea, it's pretty difficult to explain some NMR concepts clearly and fully in
a few lines of sentences. better to go back reading the books. (my Spin
Dynamics was stolen. I just remember a few things like lineshipe vs T2 at
the very early part of the book)
good to discuss
is
n
【在 t******t 的大作中提到】
: Just wanted to mention the relationship between line width and relaxation.
: Line width is related to T2 while T2
: is related to T1. If the relaxation in xy is slow, the relaxation in z is
: also slow. The longer T2 is, the sharper
: the peak is. The reason why NMR peaks are only a few Hz wide while UV-Vis
: and IR peaks are much wider and
: have to be measured by wavelength in nm is that the relaxations in these
: spectroscopy are much faster.
: The broadening caused by exchange is another story. If the excha
|
