Polymer Chemistry NMR question
$begingroup$
I am extremely new to both polymer chemistry and NMR.
I am struggling with the following question:
A proton NMR is used to attempt to quantify the molecular weight of a poly(ethylene oxide) molecule with methyoxy end groups at each terminus. If the integration of the methyl protons relative to the methylene protons gave a ratio of 1:20, what can you say about the molecular weight?
Thank you. All help is appreciate including resources for me to be able to read up on my lacking knowledge.
polymers nmr-spectroscopy
asked 4 hours ago
CarlCarl
112
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$endgroup$
add a comment |
$begingroup$
I am extremely new to both polymer chemistry and NMR.
I am struggling with the following question:
A proton NMR is used to attempt to quantify the molecular weight of a poly(ethylene oxide) molecule with methyoxy end groups at each terminus. If the integration of the methyl protons relative to the methylene protons gave a ratio of 1:20, what can you say about the molecular weight?
Thank you. All help is appreciate including resources for me to be able to read up on my lacking knowledge.
polymers nmr-spectroscopy
asked 4 hours ago
CarlCarl
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
I am extremely new to both polymer chemistry and NMR.
I am struggling with the following question:
A proton NMR is used to attempt to quantify the molecular weight of a poly(ethylene oxide) molecule with methyoxy end groups at each terminus. If the integration of the methyl protons relative to the methylene protons gave a ratio of 1:20, what can you say about the molecular weight?
Thank you. All help is appreciate including resources for me to be able to read up on my lacking knowledge.
polymers nmr-spectroscopy
asked 4 hours ago
CarlCarl
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
I am extremely new to both polymer chemistry and NMR.
I am struggling with the following question:
A proton NMR is used to attempt to quantify the molecular weight of a poly(ethylene oxide) molecule with methyoxy end groups at each terminus. If the integration of the methyl protons relative to the methylene protons gave a ratio of 1:20, what can you say about the molecular weight?
Thank you. All help is appreciate including resources for me to be able to read up on my lacking knowledge.
polymers nmr-spectroscopy
polymers nmr-spectroscopy
asked 4 hours ago
CarlCarl
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
CarlCarl
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
CarlCarl
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 4 hours ago
CarlCarl
112
asked 4 hours ago
CarlCarl
112
112
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Carl is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
1 Answer
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$begingroup$
I hope this is not a home work question. Suppose your polymer has $n$ reapeating units and capped with methyl grops at the end as you described. Thus, it should looks like following figure:
Thus it has $n$ $ce{(-CH2CH2-)}$ units and $2$ $ce{(-CH3)}$ units. Thus your $ce{(-O-CH2)}$ signal is accounted for $4n$ protons while $ce{(-O-CH2)}$ signal accounted for only $6$ protons. Thus,
$$frac{4n}{6} = frac{20}{1}$$
You may find the value of $n$ from this equation and you can calculate the molecular weight of the polymer in hand.
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
$endgroup$
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
add a comment |
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1 Answer
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1 Answer
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active
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$begingroup$
I hope this is not a home work question. Suppose your polymer has $n$ reapeating units and capped with methyl grops at the end as you described. Thus, it should looks like following figure:
Thus it has $n$ $ce{(-CH2CH2-)}$ units and $2$ $ce{(-CH3)}$ units. Thus your $ce{(-O-CH2)}$ signal is accounted for $4n$ protons while $ce{(-O-CH2)}$ signal accounted for only $6$ protons. Thus,
$$frac{4n}{6} = frac{20}{1}$$
You may find the value of $n$ from this equation and you can calculate the molecular weight of the polymer in hand.
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
$endgroup$
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
add a comment |
$begingroup$
I hope this is not a home work question. Suppose your polymer has $n$ reapeating units and capped with methyl grops at the end as you described. Thus, it should looks like following figure:
Thus it has $n$ $ce{(-CH2CH2-)}$ units and $2$ $ce{(-CH3)}$ units. Thus your $ce{(-O-CH2)}$ signal is accounted for $4n$ protons while $ce{(-O-CH2)}$ signal accounted for only $6$ protons. Thus,
$$frac{4n}{6} = frac{20}{1}$$
You may find the value of $n$ from this equation and you can calculate the molecular weight of the polymer in hand.
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
$endgroup$
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
add a comment |
$begingroup$
I hope this is not a home work question. Suppose your polymer has $n$ reapeating units and capped with methyl grops at the end as you described. Thus, it should looks like following figure:
Thus it has $n$ $ce{(-CH2CH2-)}$ units and $2$ $ce{(-CH3)}$ units. Thus your $ce{(-O-CH2)}$ signal is accounted for $4n$ protons while $ce{(-O-CH2)}$ signal accounted for only $6$ protons. Thus,
$$frac{4n}{6} = frac{20}{1}$$
You may find the value of $n$ from this equation and you can calculate the molecular weight of the polymer in hand.
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
$endgroup$
I hope this is not a home work question. Suppose your polymer has $n$ reapeating units and capped with methyl grops at the end as you described. Thus, it should looks like following figure:
Thus it has $n$ $ce{(-CH2CH2-)}$ units and $2$ $ce{(-CH3)}$ units. Thus your $ce{(-O-CH2)}$ signal is accounted for $4n$ protons while $ce{(-O-CH2)}$ signal accounted for only $6$ protons. Thus,
$$frac{4n}{6} = frac{20}{1}$$
You may find the value of $n$ from this equation and you can calculate the molecular weight of the polymer in hand.
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
answered 3 hours ago
Mathew MahindaratneMathew Mahindaratne
4138
4138
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
add a comment |
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
2
2
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
$begingroup$
Importantly, almost all polymer samples are a mixture of molecules with different chain lengths, and quantification by NMR provides an average value for the whole sample, more specifically the number-average chain length/molecular weight.
$endgroup$
– Nicolau Saker Neto
1 hour ago
add a comment |
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